Anionic α‐diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4‐cod)}] (1; Dipp=2,6‐diisopropylphenyl, cod=1,5‐cyclooctadiene), catalyze the dehydrogenation of several amine‐boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N‐heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine‐borane.