Thermo-optical and structural properties of cobalt-doped zinc oxide (ZnO) nanorods grown by chemical bath deposition were investigated. The average nanorods diameter was found to increase with cobalt doping. X-ray diffraction (XRD), Raman, and Fourier Transform Infrared (FTIR) analysis confirm the substitution of cobalt into ZnO lattice without forming any impurities at higher doping and preserving the hexagonal wurtzite structure. Variations in the absorption spectrum, band gap, photoluminescence, electronic structure by X-ray photoelectron spectroscopy (XPS), and index of refraction were analyzed at different cobalt doping levels and annealing temperatures. The thermooptic coefficient of ZnO nanorods was extracted and explained regarding cobalt doping. We will also discuss the nature of cobalt incorporation in ZnO nanorods at various doping levels.