diff --git a/internal/chart/v3/util/epoch.go b/internal/chart/v3/util/epoch.go
new file mode 100644
index 000000000..f043be6d1
--- /dev/null
+++ b/internal/chart/v3/util/epoch.go
@@ -0,0 +1,84 @@
+/*
+Copyright The Helm Authors.
+
+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
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	chart "helm.sh/helm/v4/internal/chart/v3"
+)
+
+// ParseSourceDateEpoch reads the SOURCE_DATE_EPOCH environment variable and
+// returns the corresponding time. It returns the zero time when the variable
+// is not set or is set to the empty string. An error is returned when the
+// value cannot be parsed or is negative.
+//
+// SOURCE_DATE_EPOCH is a standardised environment variable for reproducible
+// builds; see https://reproducible-builds.org/docs/source-date-epoch/
+func ParseSourceDateEpoch() (time.Time, error) {
+	v, ok := os.LookupEnv("SOURCE_DATE_EPOCH")
+	if !ok || v == "" {
+		return time.Time{}, nil
+	}
+	epoch, err := strconv.ParseInt(v, 10, 64)
+	if err != nil {
+		return time.Time{}, fmt.Errorf("invalid SOURCE_DATE_EPOCH %q: %w", v, err)
+	}
+	if epoch < 0 {
+		return time.Time{}, fmt.Errorf("invalid SOURCE_DATE_EPOCH %q: negative value", v)
+	}
+	return time.Unix(epoch, 0), nil
+}
+
+// ApplySourceDateEpoch sets the ModTime on the chart and all of its entries
+// that currently have a zero ModTime to t. It recurses into dependencies.
+// When t is the zero time this is a no-op.
+func ApplySourceDateEpoch(c *chart.Chart, t time.Time) {
+	if t.IsZero() {
+		return
+	}
+	if c.ModTime.IsZero() {
+		c.ModTime = t
+	}
+	if c.Lock != nil && c.Lock.Generated.IsZero() {
+		c.Lock.Generated = t
+	}
+	if c.Schema != nil && c.SchemaModTime.IsZero() {
+		c.SchemaModTime = t
+	}
+	for _, f := range c.Raw {
+		if f.ModTime.IsZero() {
+			f.ModTime = t
+		}
+	}
+	for _, f := range c.Templates {
+		if f.ModTime.IsZero() {
+			f.ModTime = t
+		}
+	}
+	for _, f := range c.Files {
+		if f.ModTime.IsZero() {
+			f.ModTime = t
+		}
+	}
+	for _, dep := range c.Dependencies() {
+		ApplySourceDateEpoch(dep, t)
+	}
+}
diff --git a/internal/chart/v3/util/epoch_test.go b/internal/chart/v3/util/epoch_test.go
new file mode 100644
index 000000000..0db37b3d9
--- /dev/null
+++ b/internal/chart/v3/util/epoch_test.go
@@ -0,0 +1,158 @@
+/*
+Copyright The Helm Authors.
+
+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
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"helm.sh/helm/v4/pkg/chart/common"
+	chart "helm.sh/helm/v4/internal/chart/v3"
+)
+
+func TestParseSourceDateEpoch(t *testing.T) {
+	tests := []struct {
+		name    string
+		value   string
+		set     bool
+		want    time.Time
+		wantErr bool
+	}{
+		{
+			name: "not set",
+			set:  false,
+			want: time.Time{},
+		},
+		{
+			name:  "valid epoch",
+			value: "1700000000",
+			set:   true,
+			want:  time.Unix(1700000000, 0),
+		},
+		{
+			name:    "invalid string",
+			value:   "not-a-number",
+			set:     true,
+			wantErr: true,
+		},
+		{
+			name:    "negative value",
+			value:   "-1",
+			set:     true,
+			wantErr: true,
+		},
+		{
+			name:  "zero",
+			value: "0",
+			set:   true,
+			want:  time.Unix(0, 0),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.set {
+				t.Setenv("SOURCE_DATE_EPOCH", tt.value)
+			} else {
+				prevVal, wasSet := os.LookupEnv("SOURCE_DATE_EPOCH")
+				os.Unsetenv("SOURCE_DATE_EPOCH")
+				t.Cleanup(func() {
+					if wasSet {
+						os.Setenv("SOURCE_DATE_EPOCH", prevVal)
+					}
+				})
+			}
+
+			got, err := ParseSourceDateEpoch()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("ParseSourceDateEpoch() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !got.Equal(tt.want) {
+				t.Errorf("ParseSourceDateEpoch() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestApplySourceDateEpoch(t *testing.T) {
+	epoch := time.Unix(1700000000, 0)
+
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "test",
+			Version: "0.1.0",
+		},
+		Templates: []*common.File{
+			{Name: "templates/test.yaml"},
+		},
+		Files: []*common.File{
+			{Name: "README.md"},
+		},
+	}
+
+	ApplySourceDateEpoch(c, epoch)
+
+	if !c.ModTime.Equal(epoch) {
+		t.Errorf("Chart.ModTime = %v, want %v", c.ModTime, epoch)
+	}
+	for _, f := range c.Templates {
+		if !f.ModTime.Equal(epoch) {
+			t.Errorf("Template %s ModTime = %v, want %v", f.Name, f.ModTime, epoch)
+		}
+	}
+	for _, f := range c.Files {
+		if !f.ModTime.Equal(epoch) {
+			t.Errorf("File %s ModTime = %v, want %v", f.Name, f.ModTime, epoch)
+		}
+	}
+}
+
+func TestApplySourceDateEpochPreservesExisting(t *testing.T) {
+	epoch := time.Unix(1700000000, 0)
+	existing := time.Unix(1600000000, 0)
+
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "test",
+			Version: "0.1.0",
+		},
+		ModTime: existing,
+	}
+
+	ApplySourceDateEpoch(c, epoch)
+
+	if !c.ModTime.Equal(existing) {
+		t.Errorf("Chart.ModTime = %v, want existing %v", c.ModTime, existing)
+	}
+}
+
+func TestApplySourceDateEpochZeroNoop(t *testing.T) {
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "test",
+			Version: "0.1.0",
+		},
+	}
+
+	ApplySourceDateEpoch(c, time.Time{})
+
+	if !c.ModTime.IsZero() {
+		t.Errorf("Chart.ModTime = %v, want zero", c.ModTime)
+	}
+}
diff --git a/pkg/action/package.go b/pkg/action/package.go
index 86426b412..07cfebff8 100644
--- a/pkg/action/package.go
+++ b/pkg/action/package.go
@@ -109,6 +109,13 @@ func (p *Package) Run(path string, _ map[string]any) (string, error) {
 		}
 	}
 
+	// Apply SOURCE_DATE_EPOCH for reproducible builds if set.
+	epoch, err := chartutil.ParseSourceDateEpoch()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "WARNING: %v\n", err)
+	}
+	chartutil.ApplySourceDateEpoch(ch, epoch)
+
 	var dest string
 	if p.Destination == "." {
 		// Save to the current working directory.
diff --git a/pkg/chart/v2/util/epoch.go b/pkg/chart/v2/util/epoch.go
new file mode 100644
index 000000000..f65e8c3ee
--- /dev/null
+++ b/pkg/chart/v2/util/epoch.go
@@ -0,0 +1,84 @@
+/*
+Copyright The Helm Authors.
+
+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
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	chart "helm.sh/helm/v4/pkg/chart/v2"
+)
+
+// ParseSourceDateEpoch reads the SOURCE_DATE_EPOCH environment variable and
+// returns the corresponding time. It returns the zero time when the variable
+// is not set or is set to the empty string. An error is returned when the
+// value cannot be parsed or is negative.
+//
+// SOURCE_DATE_EPOCH is a standardised environment variable for reproducible
+// builds; see https://reproducible-builds.org/docs/source-date-epoch/
+func ParseSourceDateEpoch() (time.Time, error) {
+	v, ok := os.LookupEnv("SOURCE_DATE_EPOCH")
+	if !ok || v == "" {
+		return time.Time{}, nil
+	}
+	epoch, err := strconv.ParseInt(v, 10, 64)
+	if err != nil {
+		return time.Time{}, fmt.Errorf("invalid SOURCE_DATE_EPOCH %q: %w", v, err)
+	}
+	if epoch < 0 {
+		return time.Time{}, fmt.Errorf("invalid SOURCE_DATE_EPOCH %q: negative value", v)
+	}
+	return time.Unix(epoch, 0), nil
+}
+
+// ApplySourceDateEpoch sets the ModTime on the chart and all of its entries
+// that currently have a zero ModTime to t. It recurses into dependencies.
+// When t is the zero time this is a no-op.
+func ApplySourceDateEpoch(c *chart.Chart, t time.Time) {
+	if t.IsZero() {
+		return
+	}
+	if c.ModTime.IsZero() {
+		c.ModTime = t
+	}
+	if c.Lock != nil && c.Lock.Generated.IsZero() {
+		c.Lock.Generated = t
+	}
+	if c.Schema != nil && c.SchemaModTime.IsZero() {
+		c.SchemaModTime = t
+	}
+	for _, f := range c.Raw {
+		if f.ModTime.IsZero() {
+			f.ModTime = t
+		}
+	}
+	for _, f := range c.Templates {
+		if f.ModTime.IsZero() {
+			f.ModTime = t
+		}
+	}
+	for _, f := range c.Files {
+		if f.ModTime.IsZero() {
+			f.ModTime = t
+		}
+	}
+	for _, dep := range c.Dependencies() {
+		ApplySourceDateEpoch(dep, t)
+	}
+}
diff --git a/pkg/chart/v2/util/epoch_test.go b/pkg/chart/v2/util/epoch_test.go
new file mode 100644
index 000000000..3df89ba07
--- /dev/null
+++ b/pkg/chart/v2/util/epoch_test.go
@@ -0,0 +1,158 @@
+/*
+Copyright The Helm Authors.
+
+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
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"helm.sh/helm/v4/pkg/chart/common"
+	chart "helm.sh/helm/v4/pkg/chart/v2"
+)
+
+func TestParseSourceDateEpoch(t *testing.T) {
+	tests := []struct {
+		name    string
+		value   string
+		set     bool
+		want    time.Time
+		wantErr bool
+	}{
+		{
+			name: "not set",
+			set:  false,
+			want: time.Time{},
+		},
+		{
+			name:  "valid epoch",
+			value: "1700000000",
+			set:   true,
+			want:  time.Unix(1700000000, 0),
+		},
+		{
+			name:    "invalid string",
+			value:   "not-a-number",
+			set:     true,
+			wantErr: true,
+		},
+		{
+			name:    "negative value",
+			value:   "-1",
+			set:     true,
+			wantErr: true,
+		},
+		{
+			name:  "zero",
+			value: "0",
+			set:   true,
+			want:  time.Unix(0, 0),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.set {
+				t.Setenv("SOURCE_DATE_EPOCH", tt.value)
+			} else {
+				prevVal, wasSet := os.LookupEnv("SOURCE_DATE_EPOCH")
+				os.Unsetenv("SOURCE_DATE_EPOCH")
+				t.Cleanup(func() {
+					if wasSet {
+						os.Setenv("SOURCE_DATE_EPOCH", prevVal)
+					}
+				})
+			}
+
+			got, err := ParseSourceDateEpoch()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("ParseSourceDateEpoch() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !got.Equal(tt.want) {
+				t.Errorf("ParseSourceDateEpoch() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestApplySourceDateEpoch(t *testing.T) {
+	epoch := time.Unix(1700000000, 0)
+
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "test",
+			Version: "0.1.0",
+		},
+		Templates: []*common.File{
+			{Name: "templates/test.yaml"},
+		},
+		Files: []*common.File{
+			{Name: "README.md"},
+		},
+	}
+
+	ApplySourceDateEpoch(c, epoch)
+
+	if !c.ModTime.Equal(epoch) {
+		t.Errorf("Chart.ModTime = %v, want %v", c.ModTime, epoch)
+	}
+	for _, f := range c.Templates {
+		if !f.ModTime.Equal(epoch) {
+			t.Errorf("Template %s ModTime = %v, want %v", f.Name, f.ModTime, epoch)
+		}
+	}
+	for _, f := range c.Files {
+		if !f.ModTime.Equal(epoch) {
+			t.Errorf("File %s ModTime = %v, want %v", f.Name, f.ModTime, epoch)
+		}
+	}
+}
+
+func TestApplySourceDateEpochPreservesExisting(t *testing.T) {
+	epoch := time.Unix(1700000000, 0)
+	existing := time.Unix(1600000000, 0)
+
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "test",
+			Version: "0.1.0",
+		},
+		ModTime: existing,
+	}
+
+	ApplySourceDateEpoch(c, epoch)
+
+	if !c.ModTime.Equal(existing) {
+		t.Errorf("Chart.ModTime = %v, want existing %v", c.ModTime, existing)
+	}
+}
+
+func TestApplySourceDateEpochZeroNoop(t *testing.T) {
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "test",
+			Version: "0.1.0",
+		},
+	}
+
+	ApplySourceDateEpoch(c, time.Time{})
+
+	if !c.ModTime.IsZero() {
+		t.Errorf("Chart.ModTime = %v, want zero", c.ModTime)
+	}
+}
diff --git a/pkg/downloader/manager.go b/pkg/downloader/manager.go
index 6043fbaaa..5104efbad 100644
--- a/pkg/downloader/manager.go
+++ b/pkg/downloader/manager.go
@@ -899,6 +899,13 @@ func tarFromLocalDir(chartpath, name, repo, version, destPath string) (string, e
 	}
 
 	if constraint.Check(v) {
+		// Apply SOURCE_DATE_EPOCH for reproducible builds if set.
+		epoch, epochErr := chartutil.ParseSourceDateEpoch()
+		if epochErr != nil {
+			fmt.Fprintf(os.Stderr, "WARNING: %v\n", epochErr)
+		}
+		chartutil.ApplySourceDateEpoch(ch, epoch)
+
 		_, err = chartutil.Save(ch, destPath)
 		return ch.Metadata.Version, err
 	}