Many drug discovery efforts focus on G protein-coupled receptors (GPCRs), a class of receptors that regulate many physiological processes and account for over one-third of current prescription medicines approved by the FDA. The adenosine A1 receptor (A1R) is a class A GPCR that mediates the action of the purine nucleoside adenosine and preferentially couples to the inhibitory Gi/o family of heterotrimeric G-proteins. The A1R is a particularly promising GPCR target for drug discovery, with activation of this receptor therapeutically desirable for neuropathic pain and cardiac disease. However, the progression of subtype-selective A1R agonists in the clinic has been hindered by both on- and off-target side effects. New promising avenues for pharmacological targeting of this receptor include the development of allosteric modulators and/or signal pathway ‘biased’ agonists. We have previously solved the 3.6 Å structure of the human A1R in complex with adenosine and heterotrimeric Gi2-protein determined by cryo-electron microscopy. Recently, we have solved two new structures of the same A1R-Gi2 complex to reveal the first allosteric binding site for a synthetic small molecule (VCP521) at the A1R and identify an atypical binding pose for a ‘biased’ A1R agonist (VCP746). Insights from these structures provide the first insights into the mechanisms underlying allostery and biased agonism at this important therapeutic target.