You have the option of creating your own personalized boxer, and entering a career mode, where you start off on the lowest rung in dirty, rundown gyms, as you make your way up the ropes to become the undisputed champion. Throughout your career you will have to battle many enemies, all vying for the same title. As you play, you will be able to train, improving your boxer's stats. You can hit a punching bag to increase power and speed, spar with an opponent for more stamina and agility, attack the dummy to improve chin and body, or hit the mitts to improve heart and cut. Besides career mode, you have access to the standard modes.

Fight Night 2004 features the "Total Control" system, which utilizes both sticks to give you complete percision over your boxer's moves. The right analog stick controls all the punching, and the left stick controls movement and defense/blocks.

There are several unlockables available, all of which must be earned through career mode. You can buy new clothes, entrance music, even new girls to accompany you to the ring.

The PlayStation 2 version of Fight Night 2004 supports online play via EA Sports' online network.

As with all other EA Sports titles, Fight Night 2004 utilizes the EA Sports Bio, which tracks your progress through all EA Sports games. The more games you play, the longer you play them, and the better you do translates into a higher Gamer Level. When you reach certain levels, you can unlock special rewards.