NiAl 2O 4, CuAl 2O 4, and ZnAl 2O 4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine (DEA) as a fuel. The effects of calcination temperature on structure, crystallinity, morphology, and optical properties of MAl 2O 4 (M = Ni, Cu, Zn) have been investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV–visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) spectroscopy. The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl 2O 4, CuAl 2O 4, and ZnAl 2O 4 at 1200, 1000, and 600 °C, respectively. The direct band gap of these aluminate spinels, calculated from UV-DRS spectra using the Kubelka–Munk function, is found to increase with calcination temperature. The PL spectra demonstrate that NiAl 2O 4 gives the highest blue emission intensity, while CuAl 2O 4 and ZnAl 2O 4 exhibit a very strong violet emission. During fluorescence process, the ZnAl 2O 4 emits visible light in only violet and blue regions, while NiAl 2O 4 and CuAl 2O 4 emissions extend to the green region. It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.