Episodic tremor and slip (ETS) have been correlated with rupture phenomena in subducting oceanic lithosphere at 30–45 km depth, where high V _P/V _S ratios, which suggest high‐fluid pressures, have been observed. ETS, by accommodating slip in the down‐dip portion of the subduction zone, may trigger megathrust earthquakes up‐dip in the locked section. During dehydration experiments on serpentinite (typical rock of the oceanic lithosphere) at temperatures found in nature at 30–45 km depth (400–550°C), we observe seismic signals in the form of acoustic emissions that closely resemble low frequency earthquakes, seismic tremor and regular earthquakes. Our findings support the concept that water released during dehydration reactions increases the pore pressures and can trigger ETS and regular earthquakes by reducing slip resistance.