A variety of neurotransmitters, gastrointestinal hormones, and metabolic signals are known to potentiate insulin secretion through GPCRs. We show here that beta cell-specific inactivation of the genes encoding the G protein alpha-subunits Galphaq and Galpha11 resulted in impaired glucose tolerance and insulin secretion in mice. Interestingly, the defects observed in Galphaq/Galpha11-deficient beta cells were not restricted to loss of muscarinic or metabolic potentiation of insulin release; the response to glucose per se was also diminished. Electrophysiological recordings revealed that glucose-induced depolarization of isolated beta cells was impaired in the absence of Galphaq/Galpha11, and closure of KATP channels was inhibited. We provide evidence that this reduced excitability was due to a loss of beta cell-autonomous potentiation of insulin secretion through factors cosecreted with insulin. We identified as autocrine mediators involved in this process extracellular nucleotides such as uridine diphosphate acting through the Gq/G11-coupled P2Y6 receptor and extracellular calcium acting through the calcium-sensing receptor. Thus, the Gq/G11-mediated signaling pathway potentiates insulin secretion in response to glucose by integrating systemic as well as autocrine/paracrine mediators.