We characterize structural and magnetic properties of the dilute magnetic semiconductor (In,Mn)Sb grown on GaAs (0 0 1) by molecular beam epitaxy. The films have surface features consisting of dense orthogonally oriented strain-driven hillocks. In addition, triangularly shaped hillocks, presumed to be MnSb clusters, are observed with diameters in the range of 200 nm. The density and size of these triangular hillocks depend strongly on the Mn content. X-ray scattering shows that the presence of Mn in the InSb films decreases the average lattice constant as well as the degree of relaxation of the (In,Mn)Sb films. The distribution of Mn is also investigated by cross-sectional transmission electron microscopy. Two regions are observed: a (In,Mn)Sb film with small defect density and MnSb clusters on the surface. Magnetization measurements indicate that both the (In,Mn)Sb alloy as well as the MnSb inclusions are ferromagnetic. (C) 2010 Elsevier B.V. All rights reserved.