Sylvain Marceaux began his acting training at the Municipal Theatre of Auxerre, where he took drama classes for several years before joining the Charles Dullin School in Paris for a three-year program. He then attended various workshops (Cours Florent, Théâtre de Malakoff, etc.), received performance coaching from Cyril Jarousseau (an instructor at Cours Simon), and completed his training at the Jean-Laurent Cochet School.

On stage, Sylvain has had the opportunity to explore a wide range of theatrical worlds. He has appeared in productions such as Who’s Afraid of Virginia Woolf? by Edward Albee (Municipal Theatre of Auxerre and a regional tour in Burgundy), The Madwoman of Chaillot by Jean Giraudoux (Théâtre du Campagnol, with performances at the Municipal Theatre of Auxerre), A Midsummer Night’s Dream by Shakespeare, Return to the Desert by Bernard-Marie Koltès, After the Rain by Sergi Belbel (Théâtre Daniel Sorano in Vincennes and Espace Comédia in Paris), The Little Girls of Dawn by Sylvie Chastain (script-in-hand performance at Théâtre Falguière; Théâtre de l'Épée de Bois - Cartoucherie de Vincennes), Pièce Démontée (Avignon OFF Festival 2012), The Misunderstanding by Albert Camus, For Her Beautiful Eyes by René de Obaldia (Avignon OFF Festival 2018), and The Two Timid Ones by Eugène Labiche (Paris and regional tour).

Sylvain won the P’tit Molière Award (now known as the "Cyrano Awards") in 2017 in the Best Leading Actor category for his performance in The Two Timid Ones by Eugène Labiche.

He has appeared in various television and film projects including Les Tuche 4, Menteur (feature film), the series Tout va bien (Disney+), Profilage (TF1), among others, as well as in several short films.

He is also regularly seen in commercials, music videos, web series, and guest appearances in comedic videos by content creators.