Sohn was born in The Bronx and raised in New York City. His parents were Korean immigrants. He attended CalArts and while there got a summer job working on Brad Bird's The Iron Giant. After graduating from school he worked at The Walt Disney Company and Warner Bros. before coming to Pixar. He graduated from High School in 1995.
Sohn started his career with Pixar in the art and story departments for Finding Nemo. He also worked on The Incredibles, Ratatouille and WALL-E. Sohn also performed the voice of Emile in Ratatouille. He made his directorial debut with the short film Partly Cloudy in 2009 which he also wrote. Partly Cloudy was included in the Animation Show of Shows in 2009. Sohn co-directed the English-language version of Ponyo on the Cliff by the Sea in 2009 with John Lasseter and Brad Lewis.
Sohn directed The Good Dinosaur, which was released in November 2015. He also voiced the Styracosaurus character Forrest Woodbush.
