Recent studies implicate melatonin in the antinociceptive activity of sensory neurons. However, the underlying mechanisms are still largely unknown. Here, we identify a critical role of melatonin in functionally regulating Cav3.2 T-type Ca2+ channels (T-type channel) in trigeminal ganglion (TG) neurons. Melatonin inhibited T-type channels in small TG neurons via the melatonin receptor 2 (MT2 receptor) and a pertussis toxin-sensitive G-protein pathway. Immunoprecipitation analyses revealed that the intracellular subunit of the MT2 receptor coprecipitated with G alpha(o). Both shRNA-mediated knockdown of G alpha(o) and intracellular application of QEHA peptide abolished the inhibitory effects of melatonin. Protein kinase C (PKC) antagonists abolished the melatonin-induced T-type channel response, whereas inhibition of conventional PKC isoforms elicited no effect. Furthermore, application of melatonin increased membrane abundance of PKC-eta (PKC eta) while antagonism of PKC eta or shRNA targeting PKC eta prevented the melatonin-mediated effects. In a heterologous expression system, activation of MT2 receptor strongly inhibited Cav3.2 T-type channel currents but had no effect on Cav3.1 and Cav3.3 current amplitudes. The selective Cav3.2 response was PKC eta dependent and was accompanied by a negative shift in the steady-state inactivation curve. Furthermore, melatonin decreased the action potential firing rate of small TG neurons and attenuated the mechanical hypersensitivity in a mouse model of complete Freund's adjuvant-induced inflammatory pain. These actions were inhibited by T-type channel blockade. Together, our results demonstrated that melatonin inhibits Cav3.2 T-type channel activity through the MT2 receptor coupled to novel G(beta gamma)-mediated PKC eta signaling, subsequently decreasing the membrane excitability of TG neurons and pain hypersensitivity in mice.