Jonathan Frajenberg trained at Ecole du Passage, and then at Studio 34. As an actor for the Acte6 company, he was directed by Sébastien Rajon in Peer Gynt, by Henrik Ibsen, at Théâtre 13 (2004/2005), Le Balcon, by Jean Genet (2005/2006) and Les Courtes lignes de Mr Courteline (2007/2008) at Théâtre de l’Athénée. He also performed under the direction of Frédéric Ozier in Vice(s), versa, by Thomas Middleton and William Rowley, at Sudden Théâtre, and in L’Homme qui a vu le diable, by Gaston Leroux, at Théâtre de l’Athénée, under the direction of Frédéric Jessua, in Julius Caeasar, by William Shakespeare, at Théâtre 14, in Le Baiser de sang, by Jean Aragny and Francis Neilson, and L’Atroce Volupté by Georges Neveux and Max Maurey, directed by Isabelle Siou and Frédéric Jessua at Théâtre 13.
He became part of Dramaticules in September 2008 and has since participated in all its productions : he played Fox in Un Pinocchio de moins ! (2008/09), the Second Guard in Salomé, by Oscar Wilde (2010/11), Buckingham in Richard III by William Shakespeare (2012/13), Capitaine Bordure in the Dramaticules production of Ubu Roi (2014/15), the Priest in Don Quichotte (2015/16), Laertes in Hamlet (2018/19) and the roles of Mangiafuoco, the Talking Cricket and Circus Director in Pinocchio (2020/21).