Harnessing the power of transition metal catalysis in biological settings, and especially inside living cells, can open a world of new opportunities in chemical and cell biology, as well as in biomedicine. Yet, advancing in this endeavor requires to address major chal-lenges associated to biocompatibility, transport and bioorthogonality issues, as well as the stability of the catalyst in these aqueous, crowded environments. This is especially relevant in reactions that involve the formation of organometallic intermediates that are considered labile, such as metal carbenes. Here, we demonstrate the viability of perform-ing catalytic metal carbene intermolecular transfer reactions inside live mammalian cells. In particular, we show that copper (II) catalysts can promote the intracellular an-nulation of alpha-keto diazocarbenes with ortho-amino arylamines, in a process that is initiated by the insertion of the carbene into the N-H bond of the substrate. The poten-tial of this transformation is underscored by the intracellular synthesis of a product that alters mitochondrial functions, and by demonstrating cell selective biological re-sponses using targeted copper catalysts. Considering the wide reactivity spectrum of metal carbenes, this work opens the door for significantly expanding the repertoire of reactions that can be performed in live environments and for unveiling new biological applications.