Mix the graham cracker crumbs, melted butter, and sugar. Press firmly into a 9-inch pie dish.
Chill the crust for 20 minutes.
Beat the cream cheese until smooth.
Add the sweetened condensed milk, vanilla, and lemon juice. Mix until creamy.
Fold in the chopped walnuts.
Pour the filling into the prepared crust and spread evenly.
Refrigerate for at least 4 hours (or overnight) until fully set.
Slice and serve chilled.
