We report here the synthesis of polyureas from the dehydrogenative coupling of diamines and diformamides. The reaction is catalysed by a manganese pincer complex and releases H2 gas as the only by-product making the process atom-economic and sustainable. This work advances the current state-of-the-art by replacing a toxic feedstock – diisocyanates (used to make polyureas) with a safer feedstock – diformamides and using a catalyst based on an earth-abundant metal. We also report here the physical and mechanical properties of the isolated polyureas. We suggest that the reaction proceeds via isocyanate intermediates that are formed by the manganese catalysed dehydrogenation of formamides.