The gain saturation coefficients of tensile‐strained, lattice‐matched, and compressive‐strained InGaAs/InGaAsP quantum‐well lasers (QWLs) are calculated from intrasubband relaxation times. The intrasubband relaxation times are in turn obtained within the random‐phase approximation including carrier–carrier and carrier–polar‐optical phonon interactions at room temperature. The effects of strain on the band structures are included by taking into account the strain‐dependent coupling among heavy‐hole, light‐hole, and spin‐orbit split‐off subbands on the basis of the multiband effective‐mass theory. It is demonstrated that the gain saturation coefficient in tensile‐strained QWLs is less sensitive to the amount of strain than in compressive‐strained QWLs where it markedly increases with strain.