The study of binary intermetallics formed by 3d transition metals with p elements has been of interest due to their complex magnetic properties despite their simple chemical compositions. In particular, Mn-based intermetallics have been investigated for their magnetic and physical properties that can propel these intermetallics as alternative materials for several applications Out of these compounds, MnSb crystallizes in a hexagonal NiAs-type structure in which, Mn atoms and Sb atoms occupy 2a (0, 0, 0)-sites and 2c (0.33, 0.66, 0.25) sites, respectively. In addition, two vacant 2d (0.66, 0.33, 0.25) sites are available in the structure. In the present study, the influence of addition of 3d-elements (Cr, Mn, Fe and Co) on the structural and magnetic properties of MnSb will be discussed. The nature of magnetic order and magnetic interactions were investigated using magnetic measurements employing SQUID VSM, and electronic structure calculations. The detailed analysis of magnetic measurements as well as electronic structure calculations reveal that antiferromagnetic (ferromagnetic) like state was observed at low (high) temperatures in both MnCr0.25Sb and MnFe0.25Sb However, ferrimagnetic behaviour was observed in MnCo0.25Sb. In the case of Mn1.25Sb, cluster glass and ferrimagnetic behaviour was observed.