Spinel CoAl2O4 nanoparticles were synthesized via Opuntia dillenii plant extract microwave heating method. Opuntia dillenii plant extract-assisted combustion method makes straightforward synthesis, which is alternative process of spinel nanoparticles preparation. The synthesized spinel CoAl2O4 nanoparticles was successfully characterized by powder XRD pattern, FT-IR spectra, EDX analysis, HR-SEM analysis, and VSM techniques. XRD pattern, FT-IR and EDX results established the development of spinel and single cubic phase CoAl2O4 nanocrystals. The formation of spherical shaped nanoparticles was confirmed by HR-SEM technique. VSM measurements revealed that CoAl2O4 sample have superparamagnetic behavior.