A single-phased TbCo 3 B 2 compound has been prepared by an arc-melting method. The magnetic properties and magnetocaloric effect (MCE) have been studied by the magnetization and heat capacity measurements. A large reversible magnetocaloric effect has been observed accompanied by a second-order phase transition at around Tb–Tb sublattice ordering temperature. The values of maximum magnetic entropy change (−ΔSMmax) reach 4.9 and 10.3Jkg −1 K −1 for the field change of 2 and 7T with no obvious hysteresis loss around 30K, respectively. The corresponding maximum adiabatic temperature changes (ΔTadmax) are evaluated to be 4.0 and 8.6K. The magnetic transition and the origin of large MCE in TbCo 3 B 2 were discussed.