Dos Santos is best known for his directing work on Justice League Unlimited and Avatar: The Last Airbender. He was a storyboard artist for Justice League before being promoted in the show's renamed third season. He went on to direct half of the episodes of JLU alongside fellow DCAU director Dan Riba, including the final episode "Destroyer". He joined the staff of Avatar: The Last Airbender in the middle of the show's second season as a storyboard artist, and began directing episodes in the third season, including the last two parts of the four-part season finale. He recently finished working on G.I. Joe: Resolute, an animated series initially shown only on the web but later broadcast on Cartoon Network's Adult Swim programming block. After that, Dos Santos went back to Warner Bros. Animation, where he directed two D.C. Showcase short films: The Spectre and Jonah Hex. He is now working as a co-executive producer of the animated series, The Legend of Korra.
2009: Won an Annie Award for Avatar: The Last Airbender (Best Directing in an Animated Television Production or Short Form)