The cannabinoid receptor 1 (CB1) is an inhibitory G protein-coupled receptor abundantly expressed in the central nervous system. It has rich pharmacology and largely accounts for the recreational use of cannabis. We describe efficient asymmetric syntheses of four photoswitchable Delta(9)-tetrahydrocannabinol derivatives (azo-THCs) from a central building block 3-Br-THC. Using electrophysiology and a FRET-based cAMP assay, two compounds are identified as potent CB1 agonists that change their effect upon illumination. As such, azo-THCs enable CB1-mediated optical control of inwardly rectifying potassium channels, as well as adenylyl cyclase.