The agreement, which runs through to the end of the 2010 F1 season, now includes access to promotional collateral and an increased level of branding with the Williams F1 team.
The Philips Shavers brand will now appear on the back of the team's shirts, as well as the existing brand positions on the nose of the car and on the team's overalls.
Philips Shavers also has promotional rights with both the team's drivers, Nico Rosberg and Kazuki Nakajima.
Nico Engelsman, senior vice-president at Philips Shavers, said: "Over its first two years, Philips' partnership with the AT&T Williams team has yielded significant returns for our shaving business and raised the global profile of the Philips Shavers brand.
"We are proud to be an official partner of one of Formula 1's most successful teams, a team which shares our core values of technical innovation and the pursuit of excellence.
Philips Shavers, which has sponsored the team since 2005, recently launched a new range of products under the Arcitec and Moisturising brand names.
F1 is the world's single most popular annual televised sporting event with an average of 162m TV viewers across the globe for every Grand Prix.