diff --git a/cmd/blsync/main.go b/cmd/blsync/main.go
index 39a94073045..6c8001c6a45 100644
--- a/cmd/blsync/main.go
+++ b/cmd/blsync/main.go
@@ -20,6 +20,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"path/filepath"
 	"slices"
 
 	"github.com/ethereum/go-ethereum/beacon/blsync"
@@ -44,7 +45,7 @@ func main() {
 		utils.BeaconGenesisTimeFlag,
 		utils.BeaconCheckpointFlag,
 		utils.BeaconCheckpointFileFlag,
-		//TODO datadir for optional permanent database
+		utils.DataDirFlag,
 		utils.MainnetFlag,
 		utils.SepoliaFlag,
 		utils.HoleskyFlag,
@@ -87,11 +88,18 @@ func makeRPCClient(ctx *cli.Context) *rpc.Client {
 		log.Warn("No engine API target specified, performing a dry run")
 		return nil
 	}
-	if !ctx.IsSet(utils.BlsyncJWTSecretFlag.Name) {
-		utils.Fatalf("JWT secret parameter missing") //TODO use default if datadir is specified
-	}
 
-	engineApiUrl, jwtFileName := ctx.String(utils.BlsyncApiFlag.Name), ctx.String(utils.BlsyncJWTSecretFlag.Name)
+	engineApiUrl := ctx.String(utils.BlsyncApiFlag.Name)
+	var jwtFileName string
+	if ctx.IsSet(utils.BlsyncJWTSecretFlag.Name) {
+		jwtFileName = ctx.String(utils.BlsyncJWTSecretFlag.Name)
+	} else if ctx.IsSet(utils.DataDirFlag.Name) {
+		// Use default JWT secret path in datadir
+		datadir := ctx.String(utils.DataDirFlag.Name)
+		jwtFileName = filepath.Join(datadir, "jwtsecret")
+	} else {
+		utils.Fatalf("JWT secret parameter missing")
+	}
 	var jwtSecret [32]byte
 	if jwt, err := node.ObtainJWTSecret(jwtFileName); err == nil {
 		copy(jwtSecret[:], jwt)