Circularly polarized light is central to many photonic technologies, including circularly polarized ellipsometry-based tomography, optical communication of spin information and quantum-based optical computing and information processing. To develop these technologies to their full potential requires the realization of miniature, integrated devices that are capable of detecting the chirality or ‘handedness’ of circularly polarized light. Organic field-effect transistors, in which the active semiconducting layer is an organic material, allow the simple fabrication of ultrathin, compact devices. Here we demonstrate a circularly polarized light-detecting organic field-effect transistor based on an asymmetrically pure, helically shaped chiral semiconducting molecule known as a helicene. Importantly, we find a highly specific photoresponse to circularly polarized light, which is directly related to the handedness of the helicene molecule. We believe that this opens up the possibility for the detection of the chirality of circularly polarized light in a highly integrated photonic platform.