A study of the bonding and electronic properties of intermetallics under pressure is crucial in the design and development of novel materials for useful applications. These properties are largely controlled by the underlying crystal structures. Here we investigated the high-pressure structural behavior of PtIn2 using crystal structure search calculations, which efficiently combine evolutionary algorithms and state-of-the-art density functional theory. Three new crystal structures, namely, Fe2B-type (14/mcm, Z = 2), cotunnite-type (Pnma, Z = 4), and monoclinic (C2/m, Z = 2), are proposed at about 9.4, 13.5, and 47.5 GPa, respectively. With pressure, the covalent character of the Pt-In pair interaction is found to increase because of enhancement of spd hybridization, and structural transitions are rationalized in terms of the covalency increase.