AbstractTo cope with climate change issues, a significant shift is required in worldwide energy sources. Hydrogen and bioenergy are being considered as alternatives toward a carbon neutral society, making formic acid – a hydrogen carrying product of glycerol – of interest for the valorization of glycerol. Here we investigate the plasma‐induced transformation of glycerol in an aqueous nanosecond repetitively pulsed discharge reactor. We found that the water content in the aqueous mixture fulfilled a crucial role in both the gas phase (as a source of OH radicals) and the liquid phase (as a promotor of the dissolved OH radical's mobility and reactivity). The formic acid produced was linearly proportional to the specific input energy, and the most cost‐effective production of formic acid was found with 10 % v/v glycerol in the aqueous mixture. A plausible reaction pathway was proposed, consisting of the OH radical‐driven dehydrogenation and dehydration of glycerol. The results provide a fundamental understanding of plasma‐induced transformation of glycerol to formic acid and insights for future practical applications.