Heusler compounds with heavy elements often display noncollinear magnetic structures, which can lead to phenomena such as the topological Hall effect. In this study, we report the structural, magnetic, electronic, and transport properties of IrMnGa. X-ray and neutron diffraction experiments reveal that the compound crystallizes in the cubic half-Heusler space group 216 with Y -type disorder. Manganese occupies two nonequivalent positions, causing frustration and preventing long-range magnetic order. As a consequence, a spin glass state is observed below 74 K. The spin glass state exhibits a pronounced bifurcation between field-cooled and zerofield-cooled magnetization curves, shifted hysteresis loops after field cooling, magnetic relaxation, the memory effect, absence of magnetic-ordering peaks in neutron diffraction, and a sharp cusp of the ac susceptibility. The shift of the freezing temperature as a function of ac frequency is well described by the Vogel-Fulcher law and by a critical-scaling approach indicating that IrMnGa is a canonical spin glass. Magnetotransport (including the anomalous Hall effect) and heat capacity were also investigated.