Although some sources claim that all work on the port was done by Origin themselves, the port's end credits show only Japanese people working on it.
At the time of the NES port's release, six years had elapsed since the release of the original. As such, the graphics were overhauled considerably. The new design for Ultima III was similar to that of many Japanese designed role-playing games, giving the characters an appearance stylistically similar to Japanese anime.
Given the need to adapt to an NES controller, the interface has been changed such as that most of the game's mechanical controls and player character statistics are accessible via pop-up windows, rather than through a keyboard parser. The window displaying the shifting moon-phases, however, remains unchanged. Movement is also portrayed differently in the port, with all party members represented as following a leader, instead of having the party displayed as a single sprite.