In 2004, Phillips contributed music to her first video game project, God of War. The music of God of War received five Game Audio Network Guild Awards, including Music of the Year. She quickly followed this debut with musical scores for the Charlie and the Chocolate Factory and The Da Vinci Code games, published by 2K Games. After this, Phillips composed the music for the Shrek the Third video game for Activision.
Phillips' music for the Speed Racer game for Warner Bros. Interactive Entertainment was named a finalist in the Hollywood Music Awards. After creating the music for The Maw XBLA game for Twisted Pixel Games, Phillips went on to create the music for two projects for the Maxis division of Electronic Arts: Spore Hero, and SimAnimals. Her music for Spore Hero was a finalist for The International Film Music Critics Award and the Hollywood Music in Media Award.
Phillips won a Hollywood Music in Media Award in 2010 for her music for the Legend of the Guardians video game, published by Warner Bros. Interactive Entertainment. Her music for Legend of the Guardians was also a finalist for The International Film Music Critics Award.
In 2011, Phillips began creating music for the LittleBigPlanet video game franchise for Media Molecule / Sony Computer Entertainment Europe. To date, she has created music for LittleBigPlanet 2,LittleBigPlanet 2: Toy Story (DLC), and LittleBigPlanet PS Vita.Kotaku named the score of LittleBigPlanet 2 as one of the best video game soundtracks of the year. In the article "The Best Game Music of 2011: LittleBigPlanet 2", Features Editor Kirk Hamilton praised both the collection of licensed tracks and the original score, singling out the music of composer Winifred Phillips (and particularly her track "Victoria's Lab") as his favorite original music of the game.
LittleBigPlanet 2 was a 15th Annual Interactive Achievement Awards finalist in the category of "Outstanding Achievement in Original Music Composition".LittleBigPlanet 2 was also a 2011 Game Developers Choice Awards finalist in the category of "Best Audio", which recognizes the overall excellence of audio in a game - including musical composition, orchestration, sound design, sound effects, etc. The 10th Annual Game Audio Network Guild Awards nominated the original music track "Victoria's Lab" from LittleBigPlanet 2 in the category of "Best Original Vocal - Pop".
Phillips wrote the music for the Assassin's Creed III: Liberation video game, published by Ubisoft. Together with music producer Winnie Waldron, Winifred Phillips won several awards for her work on this project. For the music composition of the Assassin's Creed III Liberation video game, Phillips won a Global Music Award for musical excellence. Winifred Phillips and Winnie Waldron won a 2012 Hollywood Music in Media Award and a GameFocus Award for the music score for Assassin's Creed III: Liberation. The main theme music of the Assassin's Creed III: Liberation video game won a G.A.N.G. Award from the Game Audio Network Guild in the category of "Best Original Vocal Song - Choral."' The music of Assassin's Creed III Liberation also received nominations in several year-end award competitions, including the GameZone Awards, the Best of IGN Awards, and the G4TV X-Play Best of 2012 Awards.
In the credits of the videogame Borderlands, Phillips is credited along with her music producer Winnie Waldron under the Audio Special Thanks section.