diff --git a/cmd/helm/flags.go b/cmd/helm/flags.go
index 8d0f644d6..379b2140d 100644
--- a/cmd/helm/flags.go
+++ b/cmd/helm/flags.go
@@ -143,6 +143,9 @@ func (p *postRendererString) Set(val string) error {
 	if val == "" {
 		return nil
 	}
+	if p.options.binaryPath != "" {
+		return fmt.Errorf("cannot specify --post-renderer flag more than once")
+	}
 	p.options.binaryPath = val
 	pr, err := postrender.NewExec(p.options.binaryPath, p.options.args...)
 	if err != nil {
diff --git a/cmd/helm/flags_test.go b/cmd/helm/flags_test.go
index 3a9d7e6ef..e55c51ce4 100644
--- a/cmd/helm/flags_test.go
+++ b/cmd/helm/flags_test.go
@@ -20,6 +20,9 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/stretchr/testify/require"
+
+	"helm.sh/helm/v4/pkg/action"
 	chart "helm.sh/helm/v4/pkg/chart/v2"
 	"helm.sh/helm/v4/pkg/release"
 	helmtime "helm.sh/helm/v4/pkg/time"
@@ -93,3 +96,24 @@ func outputFlagCompletionTest(t *testing.T, cmdName string) {
 	}}
 	runTestCmd(t, tests)
 }
+
+func TestPostRendererFlagSetOnce(t *testing.T) {
+	cfg := action.Configuration{}
+	client := action.NewInstall(&cfg)
+	str := postRendererString{
+		options: &postRendererOptions{
+			renderer: &client.PostRenderer,
+		},
+	}
+	// Set the binary once
+	err := str.Set("echo")
+	require.NoError(t, err)
+
+	// Set the binary again to the same value is not ok
+	err = str.Set("echo")
+	require.Error(t, err)
+
+	// Set the binary again to a different value is not ok
+	err = str.Set("cat")
+	require.Error(t, err)
+}