Being a racing simulation, NASCAR Thunder 2003 places the player in control of a stock car in a NASCAR race. Players battle AI drivers for race position for a preset amount of laps. As the race progresses, players are forced to make a pit stop to refuel, replace tires and repair damage.
For multiplayer support, NASCAR Thunder 2003 becomes split-screen and eliminates much of the field. Normally featuring the normal NASCAR amount of 43 drivers in a race, it is limited to 18 or less with more than one human driver. As an option, the AI drivers can be disabled, allowing the players to just race each other.
Quick Race simply allows up to four players to participate on any track and race with a specified amount of settings. After the race ends, the game returns to the main menu.
Career Mode is the most involving mode of the game. Returning from NASCAR Thunder 2002, it places the player in control of a custom Winston Cup driver, who must manage pit crew, sponsorship and research and development for 20 seasons.
Although Season Mode, like Career Mode, allows the player to play through 20 seasons, it is essentially the Quick Race mode with season standings. Unlike career mode, which starts the player with inferior equipment and pit crew, they are equal to the AI's from the start. Players have a choice to play as either existing or custom drivers, and the settings are completely customizable, unlike the limited options in Career Mode. To achieve multiplayer compatibility, it not only decreases the amount of AI drivers in a race while also randomizing them, meaning only a handful of drivers end up participating in the entire season. However, like in Quick Race, they can be disabled for a 2-4 player competition.
Thunder License is the time attack mode of the game; basically a tutorial and time trial of how to race across the included tracks.
A month after the console versions' release, a PC version of NASCAR Thunder 2003 was made available, becoming the second PC game in the series. However, despite its later release, it removes all special modes (and the entire Thunder Plate system) except for Season mode. A new testing mode is added, and 16-player multiplayer over the Internet or LAN is supported. It generally received lower scores from reviewers than the console version did.
Lightning Challenges are playable re-enactments of Winston Cup races from 1999, 2001 and 1st part of 2002. These challenges are played on all three difficulty levels. The drivers tell the players about what happened to them in the race and you have the chance to relive that moment or change history. The drivers also have a video playing behind them, showing the players of what happened to them in that situation.