Photochemical reactions of coordinatively unsaturated organopalladium complexes lacks precedent even though sterically hindered alkylphosphines that generate such species are some of the most frequently used ancillary ligands in modern Pd chemistry. Tri-tert-butylphosphine in particular has been extensively applied across many cross-coupling reactions. A related bulky monophosphine Ad3P (Ad = 1adamantyl) has also emerged recently as an effective ligand for challenging Pd-and Ni-catalysed reactions. Furthermore, complexes such as ( t Bu3P)Pd(CH3)Cl (1a) have been effective in catalysing alkene insertion (co)polymerizations in a living fashion. In this study we report on a serendipitous discovery that T-shaped organo-Pd complexes ligated by t Bu3P or Ad3P undergo efficient visible light-induced bond weakening, which induces homolysis of otherwise strong Pd(II)-C(sp 3 ) bonds under ambient conditions. Experiments and computations in this study shed light on the nature and fate of the relevant excited state involved in these processes.