diff --git a/domain/app.go b/domain/app.go
index 649fc4c..1296d64 100644
--- a/domain/app.go
+++ b/domain/app.go
@@ -2,12 +2,13 @@ package domain
 
 import (
 	"fmt"
-	"gopkg.in/yaml.v2"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 
+	"gopkg.in/yaml.v2"
+
 	"github.com/spf13/viper"
 )
 
@@ -30,6 +31,7 @@ type Mode struct {
 	StopCommand  []string `yaml:"stop-command"`
 	WorkingDir   string   `yaml:"working-dir"`
 	Dependencies []Dependency
+	Env          EnvVars
 }
 
 type Dependency struct {
@@ -37,6 +39,13 @@ type Dependency struct {
 	ModeName string `yaml:"mode"`
 }
 
+type EnvVar struct {
+	Name  string `yaml:"name"`
+	Value string `yaml:"value"`
+}
+
+type EnvVars []EnvVar
+
 func NewApp(name string, modeName string) (App, error) {
 	var err error
 
@@ -79,7 +88,7 @@ func (a *App) Start() error {
 		return fmt.Errorf("Don't know how to start %s in '%s' mode, because start-command is unset.", a.Name, a.Mode.Name)
 	}
 
-	return runCommand(a.Mode.StartCommand, a.Mode.WorkingDir)
+	return runCommand(a.Mode.StartCommand, a.Mode.WorkingDir, a.Mode.Env)
 }
 
 func (a *App) Stop() error {
@@ -90,10 +99,20 @@ func (a *App) Stop() error {
 		return fmt.Errorf("Don't know how to stop %s in '%s' mode, because stop-command is unset.", a.Name, a.Mode.Name)
 	}
 
-	return runCommand(a.Mode.StopCommand, a.Mode.WorkingDir)
+	return runCommand(a.Mode.StopCommand, a.Mode.WorkingDir, a.Mode.Env)
+}
+
+func (env EnvVars) ToStrings() []string {
+	strings := []string{}
+
+	for _, variable := range env {
+		strings = append(strings, variable.Name+"="+variable.Value)
+	}
+
+	return strings
 }
 
-func runCommand(command []string, workingDir string) error {
+func runCommand(command []string, workingDir string, env EnvVars) error {
 
 	// In the case of tools like `make`, the executable will be on the PATH
 	// and LookPath will find it.
@@ -117,6 +136,7 @@ func runCommand(command []string, workingDir string) error {
 		Stdin:  os.Stdin,
 		Stdout: os.Stdout,
 		Stderr: os.Stderr,
+		Env:    env.ToStrings(),
 	}
 
 	if viper.IsSet("verbose") {
@@ -173,6 +193,7 @@ func readConfig(appName string, sourceDir string) (Config, error) {
 			StopCommand:  mode.StopCommand,
 			Dependencies: mode.Dependencies,
 			WorkingDir:   workingDir,
+			Env:          mode.Env,
 		}
 
 		config.Modes[name] = newMode
diff --git a/domain/app_test.go b/domain/app_test.go
index 53fe7ea..949baba 100644
--- a/domain/app_test.go
+++ b/domain/app_test.go
@@ -74,4 +74,14 @@ func TestNewApp(t *testing.T) {
 			t.Errorf("Expected working dir for '%s' mode to be '%s', but it was '%s'.", modeName, expectedDir, actualDir)
 		}
 	}
+
+	// Modes' environment variables are read correctly
+
+	envVars := EnvVars{EnvVar{Name: "FOO", Value: "bar"}}
+	if expected, actual := envVars[0].Name, a.Mode.Env[0].Name; expected != actual {
+		t.Errorf("Expected env var Name to be %s, got %s", expected, actual)
+	}
+	if expected, actual := envVars[0].Value, a.Mode.Env[0].Value; expected != actual {
+		t.Errorf("Expected env var Value to be %s, got %s", expected, actual)
+	}
 }
diff --git a/domain/test-fixtures/src/foo/devon.conf.yaml b/domain/test-fixtures/src/foo/devon.conf.yaml
index 465c5d8..855d546 100644
--- a/domain/test-fixtures/src/foo/devon.conf.yaml
+++ b/domain/test-fixtures/src/foo/devon.conf.yaml
@@ -1,6 +1,9 @@
 modes:
   development:
     start-command: ["bar"]
+    env:
+      - name: FOO
+        value: bar
   unguessable:
     start-command: ["baz"]
     working-dir: "fergus"
diff --git a/example.yaml b/example.yaml
index 013c0f8..1546524 100644
--- a/example.yaml
+++ b/example.yaml
@@ -27,8 +27,11 @@ dependencies: &default_dependencies
 #
 modes:
   development:
-    start-command: ["bash", "-c", "sleep 5; echo Starting devon!"]
+    start-command: ["bash", "-c", "sleep 5; echo Starting devon with FOO=${FOO}!"]
     working-dir: .
+    env:
+      - name: FOO
+        value: bar
     dependencies: *default_dependencies
   dependency:
     start-command: ["./dev/up.sh"]