We use a combination of electrical, optical, and structural characterization techniques to determine the critical layer thickness of strained Ga1−xInxAs/InP quantum wells. Well compositions covering the entire range of strain available, from −3.8% (GaAs) to +3.2% (InAs), were investigated. We find that the critical layer thickness in this material system is unambiguously described by the classical Matthews and Blakeslee force balance model [J. Cryst. Growth 27, 118 (1974)]. Reverse leakage current of strained‐well samples grown in a p‐i‐n configuration is shown to be the most direct and reliable measure of the pseudomorphic limit.