Flannan Obé began studying comedy and singing at high school, at Cours Florent and in various Parisian conservatories; he completed this training with dance lessons (classical, modern jazz and tap). Alternating the roles of high baritone, he continues to work on the voice with Raphaël Sikorski. For several years he has also been attending the American repertoire interpretation workshops held by New York music director Christopher Denny.
In theatre, he performs in a variety of repertoires, from tragedy (Racine, Dostoïevski) to boulevardier, but it is in performances combining theatre and singing that Flannan feels like a complete artist. For seven years he was Gaston in the trio Lucienne et les Garçons who performed in Paris and at the Avignon Film Festival. Their second creation, Music-Hall, won the SPEDIDAM award at the Cérémonie des Molières 2006. In 2008 he joined Les Brigands for the operetta Arsène Lupin banquier by Mirande, Willemetz and Lattès, presented at the Théâtre de l'Athénée and then on tour in France. The following year he played Volteface in La Cour du Roi Pétaud, a funny opera by Léo Delibes; he also participated in Au Temps des Croisades by Terrasse and Franc-Nohain and, more recently in La Grande Duchesse, after Offenbach, nominated for the "Best Musical Performance" at the Molières 2015 award. In June 2010 he was Hermosa at the Opéra de Rouen in Offenbach's L'île de Tulipatan.
In 2010 he was also the protagonist of Vincent Daenen's La Nuit d'Elliot Fall, directed by Jean-Luc Revol, at the 20th Theater and on tour, nominated for the "Best Musical Performance" at the Molières 2011. In 2015 he took on the role of Count Oscar in Offenbach's Bluebeard at the Opera House in Nantes, Angers, Rennes and Le Mans. In 2016, Nancy's Opera Theatre gave him the role of John Styx in Orphée aux Enfers by Offenbach.