diff --git a/pkg/repo/chartrepo.go b/pkg/repo/chartrepo.go
index e41226fa4..bbcab2ae8 100644
--- a/pkg/repo/chartrepo.go
+++ b/pkg/repo/chartrepo.go
@@ -17,6 +17,7 @@ limitations under the License.
 package repo // import "helm.sh/helm/v4/pkg/repo"
 
 import (
+	"context"
 	"crypto/rand"
 	"encoding/base64"
 	"encoding/json"
@@ -27,6 +28,9 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"time"
+
+	"github.com/gofrs/flock"
 
 	"helm.sh/helm/v4/pkg/getter"
 	"helm.sh/helm/v4/pkg/helmpath"
@@ -106,13 +110,41 @@ func (r *ChartRepository) DownloadIndexFile() (string, error) {
 	for name := range indexFile.Entries {
 		fmt.Fprintln(&charts, name)
 	}
+
 	chartsFile := filepath.Join(r.CachePath, helmpath.CacheChartsFile(r.Config.Name))
 	os.MkdirAll(filepath.Dir(chartsFile), 0755)
-	os.WriteFile(chartsFile, []byte(charts.String()), 0644)
 
-	// Create the index file in the cache directory
 	fname := filepath.Join(r.CachePath, helmpath.CacheIndexFile(r.Config.Name))
 	os.MkdirAll(filepath.Dir(fname), 0755)
+
+	// context for lock files
+	lockCtx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	defer cancel()
+
+	// lock the charts file
+	chLock := flock.New(filepath.Join(r.CachePath, helmpath.CacheChartsFile(r.Config.Name)+".lock"))
+	chLocked, err := chLock.TryLockContext(lockCtx, 500*time.Millisecond)
+	if err == nil && chLocked {
+		defer chLock.Unlock()
+	}
+	if err != nil {
+		return "", err
+	}
+
+	// write charts files after lock
+	os.WriteFile(chartsFile, []byte(charts.String()), 0644)
+
+	// lock the index file
+	idxLock := flock.New(filepath.Join(r.CachePath, helmpath.CacheIndexFile(r.Config.Name)+".lock"))
+	idxLocked, err := idxLock.TryLockContext(lockCtx, 500*time.Millisecond)
+	if err == nil && idxLocked {
+		defer idxLock.Unlock()
+	}
+	if err != nil {
+		return "", err
+	}
+
+	// Create the index file in the cache directory
 	return fname, os.WriteFile(fname, index, 0644)
 }
 
diff --git a/pkg/repo/index.go b/pkg/repo/index.go
index c26d7581c..b93816d71 100644
--- a/pkg/repo/index.go
+++ b/pkg/repo/index.go
@@ -18,6 +18,7 @@ package repo
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -30,6 +31,7 @@ import (
 	"time"
 
 	"github.com/Masterminds/semver/v3"
+	"github.com/gofrs/flock"
 	"sigs.k8s.io/yaml"
 
 	"helm.sh/helm/v4/internal/fileutil"
@@ -103,6 +105,19 @@ func NewIndexFile() *IndexFile {
 
 // LoadIndexFile takes a file at the given path and returns an IndexFile object
 func LoadIndexFile(path string) (*IndexFile, error) {
+	lockCtx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	defer cancel()
+
+	idxLock := flock.New(filepath.Join(path + ".lock"))
+
+	idxLocked, err := idxLock.TryRLockContext(lockCtx, 500*time.Millisecond)
+	if err == nil && idxLocked {
+		defer idxLock.Unlock()
+	}
+	if err != nil {
+		return nil, err
+	}
+
 	b, err := os.ReadFile(path)
 	if err != nil {
 		return nil, err
@@ -225,6 +240,19 @@ func (i IndexFile) Get(name, version string) (*ChartVersion, error) {
 //
 // The mode on the file is set to 'mode'.
 func (i IndexFile) WriteFile(dest string, mode os.FileMode) error {
+	lockCtx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	defer cancel()
+
+	idxLock := flock.New(dest + ".lock")
+	idxLocked, err := idxLock.TryLockContext(lockCtx, 500*time.Millisecond)
+
+	if err == nil && idxLocked {
+		defer idxLock.Unlock()
+	}
+	if err != nil {
+		return err
+	}
+
 	b, err := yaml.Marshal(i)
 	if err != nil {
 		return err
@@ -237,6 +265,19 @@ func (i IndexFile) WriteFile(dest string, mode os.FileMode) error {
 //
 // The mode on the file is set to 'mode'.
 func (i IndexFile) WriteJSONFile(dest string, mode os.FileMode) error {
+	lockCtx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	defer cancel()
+
+	idxLock := flock.New(dest + ".lock")
+	idxLocked, err := idxLock.TryLockContext(lockCtx, 500*time.Millisecond)
+
+	if err == nil && idxLocked {
+		defer idxLock.Unlock()
+	}
+	if err != nil {
+		return err
+	}
+
 	b, err := json.MarshalIndent(i, "", "  ")
 	if err != nil {
 		return err