Background and Purpose: Cannabichromene (CBC) is one of the most abundant phytocannabinoids in Cannabis spp. It has modest antinociceptive and anti-inflammatory effects and potentiates some effects of Δ9-tetrahydrocannabinol in vivo. How CBC exerts these effects is poorly defined and there is little information about its efficacy at cannabinoid receptors. We sought to determine the functional activity of CBC at cannabinoid CB1 and CB2 receptors. Experimental Approach: AtT20 cells stably expressing haemagglutinin-tagged human CB1 and CB2 receptors were used. Assays of cellular membrane potential and loss of cell surface receptors were performed. Key Results: CBC activated CB2 but not CB1 receptors to produce hyperpolarization of AtT20 cells. This activation was inhibited by a CB2 receptor antagonist AM630, and sensitive to Pertussis toxin. Application of CBC reduced activation of CB2, but not CB1, receptors by subsequent co-application of CP55,940, an efficacious CB1 and CB2 receptor agonist. Continuous CBC application induced loss of cell surface CB2 receptors and desensitization of the CB2 receptor-induced hyperpolarization. Conclusions and Implications: CBC is a selective CB2 receptor agonist displaying higher efficacy than tetrahydrocannabinol in hyperpolarizing AtT20 cells. CBC can also recruit CB2 receptor regulatory mechanisms. CBC may contribute to the potential therapeutic effectiveness of some cannabis preparations, potentially through CB2 receptor-mediated modulation of inflammation.