diff --git a/packages/applications/legacy/src/controllers/helpers/fileSizeLimitError.ts b/packages/applications/legacy/src/controllers/helpers/fileSizeLimitError.ts
new file mode 100644
index 0000000000..3e08c92249
--- /dev/null
+++ b/packages/applications/legacy/src/controllers/helpers/fileSizeLimitError.ts
@@ -0,0 +1,5 @@
+export class FileSizeLimitError extends Error {
+  constructor(message: string) {
+    super(message);
+  }
+}
diff --git a/packages/applications/legacy/src/controllers/helpers/index.ts b/packages/applications/legacy/src/controllers/helpers/index.ts
index cbef267411..5755c333b7 100644
--- a/packages/applications/legacy/src/controllers/helpers/index.ts
+++ b/packages/applications/legacy/src/controllers/helpers/index.ts
@@ -13,3 +13,4 @@ export * from './yupTransformations';
 export * from './getCurrentUrl';
 export * from './getPagination';
 export * from './isSoumisAuxGF';
+export * from './fileSizeLimitError';
diff --git "a/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postCorrigerDelaiAccorde.ts" "b/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postCorrigerDelaiAccorde.ts"
index a3f2affa8f..4c126989ce 100644
--- "a/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postCorrigerDelaiAccorde.ts"
+++ "b/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postCorrigerDelaiAccorde.ts"
@@ -78,6 +78,14 @@ v1Router.post(
         );
       }
 
+      if (request.errorFileSizeLimit) {
+        return response.redirect(
+          addQueryParams(routes.GET_CORRIGER_DELAI_ACCORDE_PAGE(demandeDélaiId), {
+            error: request.errorFileSizeLimit,
+          }),
+        );
+      }
+
       const fichierRéponse = request.file && {
         contents: fs.createReadStream(request.file.path),
         filename: `${Date.now()}-${request.file.originalname}`,
diff --git "a/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postDemanderD\303\251lai.ts" "b/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postDemanderD\303\251lai.ts"
index 3e9609e826..f0dbd28b38 100644
--- "a/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postDemanderD\303\251lai.ts"
+++ "b/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postDemanderD\303\251lai.ts"
@@ -49,6 +49,14 @@ v1Router.post(
       },
     },
     async (request, response) => {
+      if (request.errorFileSizeLimit) {
+        return response.redirect(
+          addQueryParams(routes.DEMANDER_DELAI(request.body.projectId), {
+            error: request.errorFileSizeLimit,
+          }),
+        );
+      }
+
       const {
         projectId,
         justification,
diff --git "a/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postRepondreDemandeDelai.ts" "b/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postRepondreDemandeDelai.ts"
index ef6040b2b1..59248cef94 100644
--- "a/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postRepondreDemandeDelai.ts"
+++ "b/packages/applications/legacy/src/controllers/modificationRequest/d\303\251lai/postRepondreDemandeDelai.ts"
@@ -9,6 +9,7 @@ import { AccorderDateAchèvementAntérieureDateThéoriqueError } from '../../../
 import asyncHandler from '../../helpers/asyncHandler';
 import {
   errorResponse,
+  FileSizeLimitError,
   iso8601DateToDateYupTransformation,
   RequestValidationErrorArray,
   unauthorizedResponse,
@@ -57,6 +58,10 @@ v1Router.post(
           );
         }
 
+        if (request.errorFileSizeLimit) {
+          return errAsync(new FileSizeLimitError(request.errorFileSizeLimit));
+        }
+
         const file = request.file && {
           contents: fs.createReadStream(request.file.path),
           filename: `${Date.now()}-${request.file.originalname}`,
@@ -100,6 +105,18 @@ v1Router.post(
             return unauthorizedResponse({ request, response });
           }
 
+          if (error instanceof FileSizeLimitError) {
+            return response.redirect(
+              addQueryParams(
+                routes.GET_DETAILS_DEMANDE_DELAI_PAGE(request.body.modificationRequestId),
+                {
+                  ...request.body,
+                  error,
+                },
+              ),
+            );
+          }
+
           if (error instanceof RequestValidationErrorArray) {
             return response.redirect(
               addQueryParams(
diff --git a/packages/applications/legacy/src/controllers/modificationRequest/fournisseur/postChangerFournisseur.ts b/packages/applications/legacy/src/controllers/modificationRequest/fournisseur/postChangerFournisseur.ts
index f1679a05e8..e54c984141 100644
--- a/packages/applications/legacy/src/controllers/modificationRequest/fournisseur/postChangerFournisseur.ts
+++ b/packages/applications/legacy/src/controllers/modificationRequest/fournisseur/postChangerFournisseur.ts
@@ -62,6 +62,14 @@ v1Router.post(
         ),
     },
     async (request, response) => {
+      if (request.errorFileSizeLimit) {
+        return response.redirect(
+          addQueryParams(routes.CHANGER_FOURNISSEUR(request.body.projectId), {
+            error: request.errorFileSizeLimit,
+          }),
+        );
+      }
+
       const { user } = request;
       const { projectId, evaluationCarbone, justification } = request.body;
       const file = request.file && {
diff --git a/packages/applications/legacy/src/controllers/modificationRequest/postReplyToModificationRequest.ts b/packages/applications/legacy/src/controllers/modificationRequest/postReplyToModificationRequest.ts
index ebdfb0c728..70233dce5e 100644
--- a/packages/applications/legacy/src/controllers/modificationRequest/postReplyToModificationRequest.ts
+++ b/packages/applications/legacy/src/controllers/modificationRequest/postReplyToModificationRequest.ts
@@ -37,14 +37,20 @@ import { fr } from 'date-fns/locale';
 import { mediator } from 'mediateur';
 import { ModificationRequest, Project } from '../../infra/sequelize';
 
-const FORMAT_DATE = 'DD/MM/YYYY';
-
 v1Router.post(
   routes.ADMIN_REPLY_TO_MODIFICATION_REQUEST,
 
   upload.single('file'),
   ensureRole(['admin', 'dgec-validateur', 'dreal']),
   asyncHandler(async (request, response) => {
+    if (request.errorFileSizeLimit) {
+      return response.redirect(
+        addQueryParams(routes.DEMANDE_PAGE_DETAILS(request.body.modificationRequestId), {
+          error: request.errorFileSizeLimit,
+        }),
+      );
+    }
+
     const {
       user: { role },
       body: {
diff --git a/packages/applications/legacy/src/controllers/modificationRequest/postRequestModification.ts b/packages/applications/legacy/src/controllers/modificationRequest/postRequestModification.ts
index ce309a06b3..2ab21f068d 100644
--- a/packages/applications/legacy/src/controllers/modificationRequest/postRequestModification.ts
+++ b/packages/applications/legacy/src/controllers/modificationRequest/postRequestModification.ts
@@ -15,6 +15,14 @@ v1Router.post(
   ensureRole('porteur-projet'),
   upload.single('file'),
   asyncHandler(async (request, response) => {
+    if (request.errorFileSizeLimit) {
+      return response.redirect(
+        addQueryParams(routes.LISTE_PROJETS, {
+          error: request.errorFileSizeLimit,
+        }),
+      );
+    }
+
     const { projectId } = request.body;
 
     if (!validateUniqueId(projectId)) {
diff --git a/packages/applications/legacy/src/controllers/modificationRequest/producteur/postChangerProducteur.ts b/packages/applications/legacy/src/controllers/modificationRequest/producteur/postChangerProducteur.ts
index 8083ee09ef..372043c6b7 100644
--- a/packages/applications/legacy/src/controllers/modificationRequest/producteur/postChangerProducteur.ts
+++ b/packages/applications/legacy/src/controllers/modificationRequest/producteur/postChangerProducteur.ts
@@ -51,6 +51,14 @@ v1Router.post(
       },
     },
     async (request, response) => {
+      if (request.errorFileSizeLimit) {
+        return response.redirect(
+          addQueryParams(routes.GET_CHANGER_PRODUCTEUR(request.body.projetId), {
+            error: request.errorFileSizeLimit,
+          }),
+        );
+      }
+
       const { user } = request;
       const { projetId, justification, producteur } = request.body;
 
diff --git a/packages/applications/legacy/src/controllers/modificationRequest/puissance/postDemanderChangementPuissance.ts b/packages/applications/legacy/src/controllers/modificationRequest/puissance/postDemanderChangementPuissance.ts
index 6a61f4a165..5af15cfaed 100644
--- a/packages/applications/legacy/src/controllers/modificationRequest/puissance/postDemanderChangementPuissance.ts
+++ b/packages/applications/legacy/src/controllers/modificationRequest/puissance/postDemanderChangementPuissance.ts
@@ -47,6 +47,14 @@ v1Router.post(
         ),
     },
     async (request, response) => {
+      if (request.errorFileSizeLimit) {
+        return response.redirect(
+          addQueryParams(routes.DEMANDER_CHANGEMENT_PUISSANCE(request.body.projectId), {
+            error: request.errorFileSizeLimit,
+          }),
+        );
+      }
+
       const {
         body: { projectId, puissance, justification },
         user,
diff --git a/packages/applications/legacy/src/controllers/project/postCorrectProjectData.ts b/packages/applications/legacy/src/controllers/project/postCorrectProjectData.ts
index f5eb0d1aa0..feb9933c9a 100644
--- a/packages/applications/legacy/src/controllers/project/postCorrectProjectData.ts
+++ b/packages/applications/legacy/src/controllers/project/postCorrectProjectData.ts
@@ -13,13 +13,19 @@ import { upload } from '../upload';
 import { v1Router } from '../v1Router';
 import { ProjetDéjàClasséError } from '../../modules/modificationRequest';
 
-const FORMAT_DATE = 'DD/MM/YYYY';
-
 v1Router.post(
   routes.ADMIN_CORRECT_PROJECT_DATA_ACTION,
   upload.single('file'),
   ensureRole(['admin', 'dgec-validateur']),
   asyncHandler(async (request, response) => {
+    if (request.errorFileSizeLimit) {
+      return response.redirect(
+        addQueryParams(routes.PROJECT_DETAILS(request.body.projectId), {
+          error: request.errorFileSizeLimit,
+        }),
+      );
+    }
+
     if (request.body.numeroCRE || request.body.familleId || request.body.appelOffreAndPeriode) {
       return response.redirect(
         addQueryParams(routes.PROJECT_DETAILS(request.body.projectId), {
diff --git a/packages/applications/legacy/src/controllers/project/postSignalerDemandeDelai.ts b/packages/applications/legacy/src/controllers/project/postSignalerDemandeDelai.ts
index 763de1067d..52bb9c0e9d 100644
--- a/packages/applications/legacy/src/controllers/project/postSignalerDemandeDelai.ts
+++ b/packages/applications/legacy/src/controllers/project/postSignalerDemandeDelai.ts
@@ -1,6 +1,6 @@
 import fs from 'fs';
 import { ensureRole, signalerDemandeDelai } from '../../config';
-import { logger } from '../../core/utils';
+import { errAsync, logger } from '../../core/utils';
 import asyncHandler from '../helpers/asyncHandler';
 import { UnauthorizedError } from '../../modules/shared';
 import routes from '../../routes';
@@ -8,6 +8,7 @@ import {
   errorResponse,
   iso8601DateToDateYupTransformation,
   RequestValidationError,
+  FileSizeLimitError,
   unauthorizedResponse,
   validateRequestBody,
 } from '../helpers';
@@ -59,6 +60,10 @@ v1Router.post(
   asyncHandler(async (request, response) => {
     validateRequestBody(request.body, requestBodySchema)
       .asyncAndThen((body) => {
+        if (request.errorFileSizeLimit) {
+          return errAsync(new FileSizeLimitError(request.errorFileSizeLimit));
+        }
+
         const { projectId, decidedOn, status, notes, délaiCdc2022 } = body;
         const { user: signaledBy } = request;
 
@@ -93,6 +98,15 @@ v1Router.post(
           );
         },
         (error) => {
+          if (error instanceof FileSizeLimitError) {
+            return response.redirect(
+              addQueryParams(routes.ADMIN_SIGNALER_DEMANDE_DELAI_PAGE(request.body.projectId), {
+                ...request.body,
+                error,
+              }),
+            );
+          }
+
           if (error instanceof RequestValidationError) {
             return response.redirect(
               addQueryParams(routes.ADMIN_SIGNALER_DEMANDE_DELAI_PAGE(request.body.projectId), {
diff --git a/packages/applications/legacy/src/controllers/upload.ts b/packages/applications/legacy/src/controllers/upload.ts
index b7f266c136..4fb06511f0 100644
--- a/packages/applications/legacy/src/controllers/upload.ts
+++ b/packages/applications/legacy/src/controllers/upload.ts
@@ -1,4 +1,7 @@
 import multer from 'multer';
+
+import type core from 'express-serve-static-core';
+
 import { promises as fs } from 'fs';
 import { logger } from '../core/utils';
 
@@ -10,19 +13,30 @@ const uploadWithMulter = multer({
 });
 
 export const upload = {
-  single: (filename: string) => (req, res, next) => {
-    res.on('finish', async () => {
-      if (req.file) {
-        try {
-          await fs.unlink(req.file.path);
-        } catch (error) {
-          logger.error(error);
+  single:
+    (filename: string) => (req: core.Request, response: core.Response, next: core.NextFunction) => {
+      const uploadHandler = uploadWithMulter.single(filename);
+
+      uploadHandler(req, response, (err) => {
+        if (err) {
+          logger.error(err);
+          req.errorFileSizeLimit = `Le fichier ne doit pas dépasser ${FILE_SIZE_LIMIT_IN_MB} Mo`;
+          return next();
         }
-      }
-    });
 
-    return uploadWithMulter.single(filename)(req, res, next);
-  },
+        response.on('finish', async () => {
+          if (req.file) {
+            try {
+              await fs.unlink(req.file.path);
+            } catch (error) {
+              logger.error(error);
+            }
+          }
+        });
+
+        next();
+      });
+    },
   multiple: (filename?: string) => (req, res, next) => {
     return filename
       ? uploadWithMulter.array(filename)(req, res, next)
diff --git a/packages/applications/legacy/src/infra/keycloak/attachUserToRequestMiddleware.ts b/packages/applications/legacy/src/infra/keycloak/attachUserToRequestMiddleware.ts
index 055964a05f..f833ec9080 100644
--- a/packages/applications/legacy/src/infra/keycloak/attachUserToRequestMiddleware.ts
+++ b/packages/applications/legacy/src/infra/keycloak/attachUserToRequestMiddleware.ts
@@ -21,6 +21,7 @@ declare module 'express-serve-static-core' {
       accountUrl: string;
       permissions: Permission[];
     };
+    errorFileSizeLimit?: string;
   }
 }
 
diff --git a/packages/applications/legacy/src/views/components/UI/molecules/InputFile.tsx b/packages/applications/legacy/src/views/components/UI/molecules/InputFile.tsx
index f87534e479..21b30ca020 100644
--- a/packages/applications/legacy/src/views/components/UI/molecules/InputFile.tsx
+++ b/packages/applications/legacy/src/views/components/UI/molecules/InputFile.tsx
@@ -1,6 +1,8 @@
 import React from 'react';
 import { Input, LabelDescription } from '../atoms';
 
+const FILE_SIZE_LIMIT_IN_MB = 25;
+
 type InputFileProps = {
   id?: string;
   name?: string;
@@ -27,7 +29,9 @@ export const InputFile = ({
         disabled={disabled}
         className={className}
       />
-      <LabelDescription className="italic">Taille maximale du fichier : 50 Mo</LabelDescription>
+      <LabelDescription className="italic">
+        Taille maximale du fichier : {FILE_SIZE_LIMIT_IN_MB} Mo
+      </LabelDescription>
     </div>
   );
 };