Alumina (aluminum oxide) nanoparticles (AlNPs) have been categorized among the most important nano-metals, with wide applications in many fields as in food, agriculture, industry, engineering, pharmacy, medicine and others. The extensive use of AlNPs results in a massive release of them into the environment resulting in potential adverse impacts on animals and human health. Toxicokinetic studies demonstrated the rapid absorption and the systemic distribution of AlNPs to different organs. AlNPs mainly induced their toxic damage by induction of oxidative stress and mitochondrial dysfunction. Cellular accumulation of AlNPs resulted in interaction with cell components and binding with proteins and genetic materials (DNA and RNA) with producing other different chemical compounds resulting in cellular oxidative damage. Also, AlNPs induced cell death by disrupting the integrity of the mitochondrial membrane, depleting the mitochondrial thiols, activating apoptotic caspases (9 and 3) and generating more ROS. Previous in vivo and in vitro studies revealed hepato-, nephro-, myocardial, reproductive and neuro-toxic effects of AlNPs. Moreover, AlNPs exert inflammatory, apoptotic and geno-toxic effects. The aim here is to spot on previous studies demonstrating the toxic effects of AlNPs.