Quantum dots of zinc gallate (ZnGa2O4) has been synthesized by wet chemical route at a temperature of 90 °C. The structural, linear and nonlinear optical properties of ZnGa2O4 were investigated. Electronic band structure calculations are carried out for ZnGa2O4, using density functional approach and the electron effective mass, hole effective mass and band gap are evaluated as 0.27me, 16.10me and 4.58eV respectively, from which the exciton Bohr radius is estimated to be 2.72 nm. From transmission electron microscopy, size of cubic spinel ZnGa2O4 quantum dots is obtained as 8.3 nm. The theoretical band gap for ZnGa2O4 estimated using Brus equation is 4.6eV and it agrees with band gap assessed from diffuse reflectance measurements. The sample shows blue emission under UV excitation. Nonlinear optical characterization of ZnGa2O4 is done using open and closed aperture z scan technique and it shows saturable absorption and self-defocusing behavior making it suitable for display and nonlinear photonic devices.