Experimental data are presented for methane hydrate stability conditions in seawater (S ≈ 33.5‰). For the pressure range of 2.75–10.0 MPa, at any given pressure, the dissociation temperature of mcthane hydrate is depressed by approximately −1.1°C relative to the pure methane‐pure water system. These experimental results are consistent with previously reported thermodynamic predictions and experimental results obtained with artificial seawater. Collectively these results provide a minimum constraint concerning depth ranges over which methane hydrate is stable in the oceanic environment.