Magnetic properties and magnetocaloric effect (MCE) of off-stoichiometric Mn 5+ x Ge 3− x (x=−0.1 and 0.3) were studied. Depletion of Mn (x=−0.1) decreased the magnetic moment of the compound due to the reduction of the ferromagnetic Mn–Mn interactions. Mn 5.1 Ge 2.9 appeared to be near the optimal composition since Mn 5.1 Ge 2.9 exhibited increase in the magnetic moment compared to the stoichiometric compound and further Mn-enrichment beyond x=0.1 led to the formation of the weakly magnetic secondary phase. Mn 5.1 Ge 2.9 produced the maximum entropy change of 2.9Jkg −1 K −1 at 296K and the refrigeration capacity of 44.5Jkg −1 with an applied field of 10kOe, making Mn 5.1 Ge 2.9 a possible candidate magnetic refrigerant with reasonably high magnetic entropy change and negligible hysteresis.