Didier Castella was born on March 31, 1970 in Riaz and lives in the commune of Gruyères. He is married to Marie-Pierre Seydoux. He has three daughters.
He trained at the University of Fribourg, where he obtained a degree in physics (1996). In 1999, he was awarded a doctorate in physics. His political career began with his involvement in the Jeunesses PLR gruériennes (1986-1996). He was a municipal councillor (2000-2011) and vice-syndic of the commune of Gruyères (2001 to 2011).
Sworn in on May 22, 2018, he takes over the vacant Department of Institutions, Agriculture and Forests (DIAF).