Epilayer samples of GaInPN with a stoichiometry of Ga .962 In .038 P .976 N .024 and Ga .5 In .05 P .975 N .025 were grown by metallorganic chemical vapor deposition and were photoelectrochemically characterized to determine their potential to photoelectrolyze water. The materials had direct transition bandgap energies of ∼2.0 eV, as determined by photocurrent spectroscopy; however, the measured flatband potentials were several hundred millivolts too negative for unbiased water splitting. Stability was assessed by operating the electrodes as photocathodes for 24 h and qualitatively evaluated by probing the amount of surface etching with a stylus profilometer. Quantitative evaluation was done by measuring the concentration of gallium in the corrosion test electrolyte using inductively coupled plasma mass spectrometry. Results were compared to similarly treated GaP and GaInP 2 samples for context.