We report a systematic study of the effective mass of two‐dimensional (2D) holes in a series of tenp‐type GaAs/In0.20Ga0.80As/GaAs quantum well structure samples. The 2D hole density and its effective mass (m*)are independently determined from Shubnikov–de Haas and cyclotron resonance measurements at 4.2 K. We find them* increases from (0.123±0.005)meto (0.191±0.015)meas the 2D hole density is varied from 0.54×1011/cm2to 8.5×1011/cm2. The experimental data are described quantitatively in terms of a two‐band tight binding model using the valence band edge mass and strain‐induced valence band splitting as parameters. ©1995 American Institute of Physics.