Played in blistering heat, the only goal of the game was scored on 57 minutes through Angel di Maria as the Argentines retained the Olympic title they won in Athens four years ago.
It was a match of few clear-cut chances, with the South Americans just shaving it on possession, and it was perhaps their greater experience with the likes of Lionel Messi, Sergio Aguero and Juan Roman Riquelme that decided the game.
Di Maria netted his winner after being set free down the left by Messi and, with Nigerian goalkeeper Ambrose Vanzekin advancing to close him down, he chipped the ball into an empty net.
Nigeria tried to push forward in the closing stages, with Victor Anichebe twice going close, but Argentina held on for the win – and a repeat of that Athens Gold.
Meanwhile, a brace from striker Jo and a goal from Diego sealed a comfortable 3-0 victory for Brazil over Belgium in the Bronze medal match played in Shanghai on Friday.