The exponential increase in global energy and clean energy demands lead to the necessity for development of efficient photocatalyst for hydrogen evolution. Herein, photocatalytic hydrogen evolution activity with nano-structured ZnFe2-xGaxO4(0 ≤x ≤ 2) solid solution samples synthesized by citrate-gel method at 550°C is reported. The prepared materials have been characterized for their structure and optical properties. The formation of solid solution with spinel type structure in the complete range of composition and a systematically decreasing trend of unit cell parameters with increasing Ga3+ concentration is observed from powder XRD studies. The band gap of these solid solutions could be tuned from 1.9 to 3.1 eV by increasing the Ga3+ concentration. Without any co-catalyst, ZnFe2O4 shows poor catalytic activity (378μmolh−1g−1) for photocatalytic hydrogen evolution from water. Whereas its activity enhances with loading of co-catalyst and touches a maximum activity of 3089μmolh−1g−1 with loading 1 wt% of Pt. The catalytic activity increases systematically with increasing Ga concentration in the solid solutions and reaches to 3989μmolh−1g−1 for ZnGa2O4 nanomaterials. Electrochemical impedance spectroscopic and transient photocurrent measurements also support the observed increasing trend. The lower catalytic activity of ZnFe2O4 has been attributed to the faster e-h recombination due to lower band gap and inherent oxygen vacancies. A smaller amount of oxygen vacancies and segregated ZnO phase observed in Ga substituted ZnFe2O4 samples favor the e-h pair separation and that facilitate the hydrogen generation from water.