Hybrid organic-inorganic perovskites exhibit strong spin-orbit coupling(1), spin-dependent optical selection rules(2,3) and large Rashba splitting(4-8). These characteristics make them promising candidates for spintronic devices(9) with photonic interfaces. Here we report that spin polarization in perovskites can be controlled through chemical design as well as by a magnetic field. We obtain both spin-polarized photon absorption and spin-polarized photoluminescence in reduced-dimensional chiral perovskites through combined strategies of chirality transfer and energy funnelling. A 3% spin-polarized photoluminescence is observed even in the absence of an applied external magnetic field owing to the different emission rates of sigma(+) and sigma(-) polarized photoluminescence. Three-dimensional perovskites achieve a comparable degree of photoluminescence polarization only under an external magnetic field of 5 T. Our findings pave the way for chiral perovskites as powerful spintronic materials.