diff --git a/CHANGELOG.md b/CHANGELOG.md
index cff9187..beb90d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@ dev:
   - add "--generate-keystore" option for "account derive"
   - update "validator exit" command to be able to generate multiple exits
   - support for 12-word and 18-word mnemonics with single-word (no whitespace) passphrases
+  - add JSON output for "validator expectation"
 
 1.30.0:
   - add "chain spec" command
diff --git a/cmd/validator/expectation/command.go b/cmd/validator/expectation/command.go
index ff33a8e..c8ddf67 100644
--- a/cmd/validator/expectation/command.go
+++ b/cmd/validator/expectation/command.go
@@ -15,9 +15,12 @@ package validatorexpectation
 
 import (
 	"context"
+	"encoding/json"
+	"fmt"
 	"time"
 
 	eth2client "github.com/attestantio/go-eth2-client"
+	"github.com/hako/durafmt"
 	"github.com/pkg/errors"
 	"github.com/spf13/viper"
 )
@@ -26,6 +29,7 @@ type command struct {
 	quiet   bool
 	verbose bool
 	debug   bool
+	json    bool
 
 	// Beacon node connection.
 	timeout                  time.Duration
@@ -38,18 +42,43 @@ type command struct {
 	// Data access.
 	eth2Client         eth2client.Service
 	validatorsProvider eth2client.ValidatorsProvider
-	activeValidators   int
 
-	// Output.
+	// Results.
+	res *results
+}
+
+type results struct {
+	activeValidators          uint64
 	timeBetweenProposals      time.Duration
 	timeBetweenSyncCommittees time.Duration
 }
 
+type resultsJSON struct {
+	ActiveValidators          string `json:"active_validators"`
+	TimeBetweenProposals      string `json:"time_between_proposals"`
+	SecsBetweenProposals      string `json:"secs_between_proposals"`
+	TimeBetweenSyncCommittees string `json:"time_between_sync_committees"`
+	SecsBetweenSyncCommittees string `json:"secs_between_sync_committees"`
+}
+
+func (r *results) MarshalJSON() ([]byte, error) {
+	data := &resultsJSON{
+		ActiveValidators:          fmt.Sprintf("%d", r.activeValidators),
+		TimeBetweenProposals:      durafmt.Parse(r.timeBetweenProposals).LimitFirstN(2).String(),
+		SecsBetweenProposals:      fmt.Sprintf("%d", int64(r.timeBetweenProposals.Seconds())),
+		TimeBetweenSyncCommittees: durafmt.Parse(r.timeBetweenSyncCommittees).LimitFirstN(2).String(),
+		SecsBetweenSyncCommittees: fmt.Sprintf("%d", int64(r.timeBetweenSyncCommittees.Seconds())),
+	}
+	return json.Marshal(data)
+}
+
 func newCommand(_ context.Context) (*command, error) {
 	c := &command{
 		quiet:   viper.GetBool("quiet"),
 		verbose: viper.GetBool("verbose"),
 		debug:   viper.GetBool("debug"),
+		json:    viper.GetBool("json"),
+		res:     &results{},
 	}
 
 	// Timeout.
diff --git a/cmd/validator/expectation/output.go b/cmd/validator/expectation/output.go
index de2b67a..2636269 100644
--- a/cmd/validator/expectation/output.go
+++ b/cmd/validator/expectation/output.go
@@ -1,4 +1,4 @@
-// Copyright © 2021 Weald Technology Trading.
+// Copyright © 2021, 2023 Weald Technology Trading.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -15,24 +15,42 @@ package validatorexpectation
 
 import (
 	"context"
+	"encoding/json"
+	"fmt"
 	"strings"
 
 	"github.com/hako/durafmt"
 )
 
-func (c *command) output(_ context.Context) (string, error) {
+func (c *command) output(ctx context.Context) (string, error) {
 	if c.quiet {
 		return "", nil
 	}
 
+	if c.json {
+		return c.outputJSON(ctx)
+	}
+	return c.outputTxt(ctx)
+}
+
+func (c *command) outputJSON(_ context.Context) (string, error) {
+	data, err := json.Marshal(c.res)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s\n", string(data)), nil
+}
+
+func (c *command) outputTxt(_ context.Context) (string, error) {
 	builder := strings.Builder{}
 
 	builder.WriteString("Expected time between block proposals: ")
-	builder.WriteString(durafmt.Parse(c.timeBetweenProposals).LimitFirstN(2).String())
+	builder.WriteString(durafmt.Parse(c.res.timeBetweenProposals).LimitFirstN(2).String())
 	builder.WriteString("\n")
 
 	builder.WriteString("Expected time between sync committees: ")
-	builder.WriteString(durafmt.Parse(c.timeBetweenSyncCommittees).LimitFirstN(2).String())
+	builder.WriteString(durafmt.Parse(c.res.timeBetweenSyncCommittees).LimitFirstN(2).String())
 	builder.WriteString("\n")
 
 	return builder.String(), nil
diff --git a/cmd/validator/expectation/process.go b/cmd/validator/expectation/process.go
index 2faad08..c4df022 100644
--- a/cmd/validator/expectation/process.go
+++ b/cmd/validator/expectation/process.go
@@ -1,4 +1,4 @@
-// Copyright © 2021 Weald Technology Trading.
+// Copyright © 2021, 2023 Weald Technology Trading.
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -31,7 +31,7 @@ func (c *command) process(ctx context.Context) error {
 	}
 
 	if c.debug {
-		fmt.Printf("Active validators: %d\n", c.activeValidators)
+		fmt.Printf("Active validators: %d\n", c.res.activeValidators)
 	}
 
 	if err := c.calculateProposalChance(ctx); err != nil {
@@ -59,7 +59,7 @@ func (c *command) calculateProposalChance(ctx context.Context) error {
 		return errors.New("SECONDS_PER_SLOT of incorrect type")
 	}
 
-	c.timeBetweenProposals = slotDuration * time.Duration(c.activeValidators) / time.Duration(c.validators)
+	c.res.timeBetweenProposals = slotDuration * time.Duration(c.res.activeValidators) / time.Duration(c.validators)
 
 	return nil
 }
@@ -109,12 +109,12 @@ func (c *command) calculateSyncCommitteeChance(ctx context.Context) error {
 		return errors.New("EPOCHS_PER_SYNC_COMMITTEE_PERIOD of incorrect type")
 	}
 
-	periodsBetweenSyncCommittees := uint64(c.activeValidators) / syncCommitteeSize
+	periodsBetweenSyncCommittees := c.res.activeValidators / syncCommitteeSize
 	if c.debug {
 		fmt.Printf("Sync committee periods between inclusion: %d\n", periodsBetweenSyncCommittees)
 	}
 
-	c.timeBetweenSyncCommittees = slotDuration * time.Duration(slotsPerEpoch*epochsPerPeriod) * time.Duration(periodsBetweenSyncCommittees) / time.Duration(c.validators)
+	c.res.timeBetweenSyncCommittees = slotDuration * time.Duration(slotsPerEpoch*epochsPerPeriod) * time.Duration(periodsBetweenSyncCommittees) / time.Duration(c.validators)
 
 	return nil
 }
@@ -157,7 +157,7 @@ func (c *command) setup(ctx context.Context) error {
 	for _, validator := range validators {
 		if validator.Validator.ActivationEpoch <= currentEpoch &&
 			validator.Validator.ExitEpoch > currentEpoch {
-			c.activeValidators++
+			c.res.activeValidators++
 		}
 	}