The present study reports a green chemistry approach for the biosynthesis of nano-zinc aluminate by a microwave method using high purity metal nitrates and aloe vera plant extract. Aloe vera extract simplifies the process and provides an alternative process for a simple and economical synthesis of nanocrystalline zinc aluminate. It is prepared by conventional and microwave method by with and without using the plant extract for comparison purpose. The obtained nanomaterials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HR-TEM) diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The XRD confirmed the formation of cubic structure of zinc aluminate. The formation of zinc aluminate phase is also confirmed by FT-IR. The change in morphology from nanorods to nanosheets from the conventional method to microwave method is clearly shown by HR-SEM. The optical properties were determined by DRS and PL spectra. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.