As a teenager, Christian Hecq was passionate about physics and for a while dreamed of specializing in alternative energy sources. At the same time, he was also already active in amateur theatre, and finally enrolled in the Institut national supérieur des arts du spectacle de Bruxelles. In 1987, Isabelle Pousseur directed him in Marivaux’s Les Acteurs de bonne foi at the Théâtre national de Belgique. George Bernard Shaw’s Cesar and Cleopatra; Claude Mauriac’s Le Cirque and Kafka’s Metamorphosis directed by Steven Berkoff followed. In 1989, he won the Eve Award for Belgian best young actor. He began working with director Daniel Mesguich in 1992, with Boulevard du boulevard at the Théâtre de la Métaphore in Lille, a play that was taken over by the Théâtre du Rond-Point in Paris in 2006. Their collaboration continued in 1994 with L’Histoire qu’on ne connaîtra jamais by Hélène Cixous at the Théâtre de la Ville and again, in 2001, with Molière’s Dom Juan at the Théâtre de l’Athénée. In 1997, he directed Achille et Léonie, a comedy duo selected to represent Belgium at the 20th Festival du cirque de demain. In 2000, he won the Molière Award for Best Newcomer in Theatre for playing in Feydeau’s La Main passe directed by Gildas Bourdet. As part of the Compagnie Philippe Genty, he performed in shows combining visual arts and puppetry.

Christian Hecq has been pensionnaire of the Comédie-Française since 2008, where he made his debut in Beaumarchais’s Le Mariage de Figaro directed by Christophe Rauck. He was appointed the 525th sociétaire of the Company on the 1st of January 2013. Whether Gubetta in Hugo’s Lucrezia Borgia directed by Denis Podalydès; Nonancourt in Labiche’s An Italian Straw hat (Un chapeau de paille d'Italie) by Giorgio Barberio Corsetti; Sosie in Molière’s Amphitryon by Jacques Vincey; Monsieur Orgon in Marivaux’s Le Jeu de l'amour et du hasard by Galin Stoev; or Mathieu in Feydeau’s Free Exchange Hotel (L’Hôtel du Libre-Échange) by Isabelle Nanty, Christian Hecq performs them in such a singular way so as to make each a landmark role. In 2010, Muriel Mayette-Holtz staged him in Mystère Bouffe et Fabulages de Dario Fo, while Philippe Meyer directed him in the cabaret Chansons des jours avec et chansons des jours sans. His hilarious interpretation of Bouzin in Feydeau’s Un fil à la patte directed by Jérôme Deschamps earned him a Molière Award for Best Actor in 2011. He was equally acclaimed in 2015 for playing an extreme and surrealist Lunardo in Goldoni’s The Boors (Les Rustres) staged by Jean-Louis Benoit.

In 2016, Christian Hecq and Valérie Lesort adapted and directed Jules Verne’s Twenty Thousand Leagues Under the Sea (20 000 lieues sous les mers), in which he also played Nemo and for which he was nominated for four Molière Awards. He won the Award for Visual Creation.

His Portrait d'acteur has been reveal during the first Nuit du jeu broadcasted on decembre 20, 2022. The interveiw is available on YouTube.

His filmography includes The Eighth Day (Le Huitième Jour) by Jaco Van Dormaël; Nine Month Stretch (9 mois ferme) by Albert Dupontel; Cézanne and I (Cézanne et moi) by Danièle Thompson; Knock by Loraine Lévy and Animal Kingdom: Let’s Go Ape (Pourquoi j’ai pas mangé mon père) by Jamel Debbouze. On television, he appeared in La Parure by Claude Chabrol, Crimes en série by Patrick Dewolf and Spiral (Engrenages).

Christian Hecq is Knight of the Order of Arts and Letters (chevalier dans l'ordre des Arts et des Lettres). He first appeared in Le Petit Larousse dictionary in 2017.

During the 2018/2019 season, Christian Hecq will perform in the rerun of Victor Hugo’s Lucrezia Borgia by Denis Podalydès, in the rerun of Jules Verne’s Twenty Thousand Leagues Under the Sea written and directed with Valérie Lesort and in the rerun of Feydeau’s Free Exchange Hotel by Isabelle Nanty.