Neurotensin (NT) is a tridecapeptide that interacts with three NT receptors, NTS1, NTS2 and NTS3. Whereas NT has been reported to modulate GABAergic activity in the brain, the underlying cellular and molecular mechanisms of NT are elusive. Here, we examined the effects of NT on GABAergic transmission and the involved cellular and signaling mechanisms of NT in the hippocampus. Application of NT dose-dependently increased the frequency of sIPSCs recorded from CA1 pyramidal neurons with no effects on the amplitude of sIPSCs. NT did not change either the frequency or the amplitude of mIPSCs recorded in the presence of tetrodotoxin. Triple immunofluorescent staining of recorded interneurons demonstrated the expression of NTS1 on GABAergic interneurons. NT increased action potential firing rate but decreased the afterhyperpolarization (AHP) amplitude in identified CA1 interneurons. Application of L-type calcium channel blockers (nimodipine and nifedipine) abolished NT-induced increases in action potential firing rate and sIPSC frequency and reduction in AHP amplitude suggesting that the effects of NT are mediated by interaction with L-type Ca²⁺ channels. NT-induced increase in sIPSC frequency was blocked by application of the specific NTS1 antagonist SR48692, the PLC inhibitor U73122, the IP₃ receptor antagonist 2-APB, and the PKC inhibitor GF109203X suggesting that NT increases GABA release via a PLC pathway. Our results provide a cellular mechanism by which NT controls GABAergic neuronal activity in hippocampus.