Alumina nanoparticles (AlNP) were synthesized from aluminium nitrate using extracts of tea, coffee and triphala—a well known herbal plant as well as a non-toxic and eco—friendly green material. The synthesis was carried out taking 1:4 ratio of metal salt and these extracts under microwave irradiations at 540 W, which gave better yield of nanoparticles. Water was taken as solvent medium. The formations of AlNP were initially monitored by the colour changes occurring in the reaction mixture during the incubation period. As synthesized nanoparticles were characterized by scanning electron microscope (SEM), UV–Visible (UV–Vis) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The AlNP were found to be spherical in shape in case of tea and coffee extracts with a size of 50–200 nm and to be oval shaped in case of triphala extract with an average size of 200–400 nm. The formation of AlNP with the microwave-assistance using these plant extracts has proved to be very faster than any other methods. In addition, excellent reproducibility of these nanoparticles, without the use of any additional capping agent or stabilizer will have great advantages in comparison with microbial synthesis, avoiding all the tedious and hygienic complications.