Abstract Helicity-dependent all-optical magnetization switching in bismuth, gallium-substituted rare-earth iron garnet thin films is hypothesized to be achievable near the angular momentum compensation composition. In this study, highly crystalline,(100)-oriented Nd 0.5 Bi 2.5 Fe 5-x Ga x O 12 (Bi,Ga:NIG) thin films with x = 0 to 2 were successfully synthesized on Gd 3 Ga 5 O 12 (100) substrates via metal-organic decomposition to systematically investigate the compensation boundaries. Prepared thin films were systematically evaluated using magneto-optical spectroscopy and ferromagnetic resonance (FMR) measurement. Magneto-optical measurements revealed a large Faraday rotation angle, accompanied by a distinct spectral sign reversal between Ga substitution levels of x=1.3 ~ 1.4, confirming the presence of a magnetization compensation composition for the iron sublattice of the prepared films. In addition, FMR analysis showed an increased gyromagnetic ratio as Ga substitution increased from 0.6 to 0.7 establishing the existence of an angular momentum compensation composition for Bi,Ga:NIG thin films at room temperature.