He attended CalArts and while there got a summer job working on Brad Bird"s The Iron Giant.
After school he worked at The Walt Disney Company and Warner Brothers before coming to Pixar. Sohn started his career with Pixar in the art and story departments for Finding Nemo. He also worked on The Incredibles, Ratatouille and WALL-East. 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.
Russell, the boy in Up, was based on Sohn. He voiced Russell in the corresponding short,, and "Squishy" in Monsters University.
Sohn directed The Good Dinosaur, which was released in November 2015.
He also voiced the Styracosaurus character Forrest Woodbush. Personal life Sohn is married to artist Anna Chambers, whom he met at CalArts.