In this work we report on the structural, magnetic and magnetocaloric properties of polycrystalline Ho1-xErxCo2 solid solutions (0.1 <= x <= 0.5). Powder X-ray diffraction study at room temperature showed that the compounds crystallize in the C15 cubic Laves phase structure (MgCu2 type). The magnetization behavior and magnetic transitions are analyzed in terms of Landau theory. Curie temperatures (Tc) of Ho1-xErxCo2 decrease from 72 K in Ho0.9Er0.1Co2 to 50 K in Ho0.5Er0.5Co2. The magnetic measurements show that the compounds undergo a first-order phase transition from paramagnetic to a ferrimagnetic state at T. A large isothermal entropy change AS is calculated from the magnetization curves using the thermodynamic Maxwell's relations observed for Ho1-xErxCo2 with all Er concentrations under study. The maximum effect of similar to 5.4 J mol(-1) K-1 is found in Ho0.6Er0.4CO2 (T-C = 56 K) as the field changes from 0 to 3 T. (C) 2012 Elsevier B.V. All rights reserved.