Three drivers would drive the FW25 in the 2003 season, with Marc Gené replacing regular racer Ralf Schumacher for the Italian Grand Prix after the German suffered a large testing accident at Monza's Lesmo 1 corner prior to that race.

Montoya cited the FW25 as a favourite of his, praising the balance and the driveability with the powerful BMW engine which suited his aggressive driving style.

[6] A change to the front tyre width (resulting from a protest lodged by Michelin's rivals Bridgestone, through the Ferrari team, after the Hungarian Grand Prix) caused controversy through the paddock, with Williams tipped to lose their competitive edge after that race due to a slimmer tyre design being raced at the Italian Grand Prix at Monza being seemingly at odds with the wider tyre that Williams brought with great effect to the Monaco Grand Prix.

New sponsors including Hewlett-Packard, who bought Compaq in previous year and a brewery brand Budweiser.

At the German Grand Prix, the "Budweiser" logo was simplified as "Bud" due to the licensing issues from its parent company, Anheuser-Busch.