A complete reimagining of the series' formula, NFSU offered a career mode featuring a storyline, and a garage mode that allowed players to fully customize their cars with a large variety of brand-name performance and visual upgrades. All races take place in a generic city at night (though the city bears some resemblance to New York, San Francisco and Los Angeles). Instead of hundred-thousand dollar exotics, Underground featured vehicles associated with the Import Scene. This, plus the increasingly arcade-like controls, became points of controversy for Need for Speed fans. Despite this, Underground was commercially very successful, and inspired a sequel.

It is rumored that the car manufacturers were very strict in how their vehicles were to be portrayed in this game, especially considering the "illegal street racing" reputation of the tuner culture. EA took some effort in making the races appear as sanctioned racing events, and included a public service announcement in the game's introduction. In addition, vehicles do not have damage models.