We report on the high irreversible adiabatic temperature change of −8 K in a magnetic field change of 1.95 T in the Heusler compound Ni45.7Mn36.6In13.5Co4.2 showing a first-order magnetostructural transition. Due to the large thermal hysteresis of 10 K, this high ΔTad cannot be obtained in a cyclic way but still the reversible magnetocaloric effect amounts to −3 K—an unexpectedly high value which compares to the ΔTad of La(Fe,Si,Co)13. In order to reveal the nature of this high reversible magnetocaloric effect, in-situ temperature dependent optical microscopy of minor loops of thermal hysteresis has been done.