After graduating from the Cours Florent and the Conservatoire, Sébastien Thiéry embarked on a life as an actor. He appeared in various films by Bertrand Tavernier, Josée Dayan, Gérard Jugnot, and Alain Chabat.

At 30, he decided to begin writing for the theater. His first play, Sans ascenseur (Without Elevator), was directed by Jean-Michel Ribes at the Théâtre du Rond-Point. He played himself in the play, as he would in most of the subsequent ones. He wrote La Fâche, also directed at the Théâtre du Rond-Point by Gilles Cohen in 2005, and Dieu habite Düsseldorf, produced at the Théâtre des Mathurins by Christophe Lidon in 2006.

Writer and performer of the Canal+ series Chez Maman, he wrote 300 episodes between 2004 and 2005. He also filmed hidden cameras for Stéphane Bern’s show La vie de Sébastien Thiéry on the same channel.

He returned to writing for the theater, and Piggy Bank was directed by Anne Bourgeois in 2009 at the Théâtre Hébertot, winning the Prix Barrière in 2008 and two Molières in 2009 – Best Actor for Patrick Chesnais and Best Comedy Play. In 2009, Who’s Mr Schmitt? was staged at the Théâtre de la Madeleine by José Paul, starring Richard Berry. In 2011, he directed and performed The Beginning of the End at the Théâtre des Variétés alongside Jonathan Lambert. In 2012, he starred in Courteline, Amour noir, directed by Jean-Louis Benoit. Then, Pierre Arditi and Évelyne Buyle performed Falling from the trees, directed by Bernard Murat at the Théâtre Édouard VII. In September 2013, Jean-Michel Ribes directed The Origin of the World at the Théâtre du Rond-Point. In December, Jean-Louis Benoit directed Tilt! with Bruno Solo. In 2014, he created Two Stark Naked Men at the Théâtre de la Madeleine, with François Berléand, Isabelle Gélinas and himself, in a production by Ladislas Chollat. In 2015, he created Momo at the Théâtre de Paris, with Muriel Robin, François Berléand, and himself, in a production by Ladislas Chollat, which he adapted into a film in 2017.
In 2017, he created Ramses II at the Bouffes Parisiens with Éric Elmosnino, François Berléand, and Evelyne Buyle, and in 2019, Eight Euros an Hour at the Théâtre Antoine, with Dany Boon and Valérie Bonneton, directed by Stéphane Hillel. This was followed by the revival of Who is Mr. Schmitt? in 2021 with Stéphane de Groodt and Valérie Bonneton at the Théâtre Edouard 7.
Then, TDEmain la revanche with Gaspard Proust in 2022 at the Théâtre Antoine. In September 2023, Yvan Attal and Noémie Lvovsky will premiere Video Club, also at the Théâtre Antoine. Then, in September 2024, Bernard Campan will play the lead role in Check Up, which could be described as a “hospital comedy.” In January 2026, Arnaud Ducret and Maxime d’Aboville will revive Cochons d’Guinée, which premiered in 2009. All of these plays are regularly performed abroad.