The first hybrid phototransistors are reported where the performance of a network of photoactive CH3NH3PbI3 nanowires is enhanced by CVD-grown monolayer graphene. These devices show responsivities as high as ≈2.6 × 106 A W-1 in the visible range, showing potential as room-temperature single-electron detectors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.