Contra was released for the Nintendo Entertainment System in North America in February 1988. This version was produced in-house by Konami and features several differences from the arcade release in order to better suit the NES's hardware. The game can be played by up to two players, but due to the graphical limitations of the NES, Bill and Lance lost their individualized character designs. Instead, they are both depicted as shirtless commandos distinguished by the colors of their pants (blue pants for the first player and red pants for the second). When one player loses all of their lives, they are given the option to use the other player's stock to keep fighting.
The power-up icons for the Machine Gun and Laser Gun were also changed and are now represented by letter-based falcon symbols like the other weapons. The Rapid Bullets and Barrier power-ups are also more common in this version. The NES version introduces a seventh item that clears the screen of all on-screen enemies when obtained, although it only appears in one area throughout the entire game.
The NES version consists of eight stages, which are structured a bit differently from the arcade game. Stage 1 (the jungle) starts similarly to its arcade counterpart, but the level is longer and there's an added segment where the player must jump over a couple of bottomless pits just before reaching the gate. Stage 2 combines the first base stage and the subsequent battle in the core of the base into one level, whereas Stage 4 does the same for the second base and its core. Both base stages no longer have a time limit and feature a completely linear layout compared to the maze-like designs of their arcade counterparts. Stage 3 (the waterfall) is also longer and has a different boss at the end: instead of destroying a sensor, the player fights an alien statue that shoots fireballs from its mouth and limbs. Stages 5 through 8 are based on the various areas that composed the final stage of the arcade version (a snowfield, an energy zone, a hangar and the alien's lair). Each of these stages end with a showdown against an enemy boss.
Contra was one of the early NES games to feature the Konami Code. Inputting the code at the title screen starts the player with thirty lives instead of the usual three. The cheat will be in effect as well when the player runs out of lives and uses a continue to retry a stage.
When the NES version of Contra was localized for the North American market, certain details of the game's background story were altered. The year of the setting was changed from 2633 to 1987 (the year of the arcade version's release) and the location was moved from the Galuga Islands to the Amazon. Bill and Lance were also given the codenames of Mad Dog and Scorpion.