Simon Guélat was born in Jura, Switzerland, in 1985. He trained as an actor at the Haute École de Théâtre de Suisse Romande, graduating in 2007. Following his graduation, he worked with several French-speaking directors and stage directors, including Ursula Meier, Lionel Baier, Francis Reusser, Matthieu Bertholet, and Eric Vigner.

In 2010, he moved to Paris. Alongside his acting career, Simon Guélat wrote and directed his first short film, Cabane, produced by Les Films du Bélier. The film was selected for numerous festivals, including Locarno and Clermont-Ferrand.

In 2016, he pursued documentary filmmaking at the Ateliers Varan and directed the short documentary Chahine, which was selected for the Visions du Réel Festival in Nyon. He is currently preparing his second fiction short film, Aline, and plays the role of Markus in Robin Campillo's feature film 120 Battements par Minute, which won the Grand Prix at the 2017 Cannes Film Festival.