Significant progress in the research of mammalian target of rapamycin (mTOR) in recent years, has greatly enhanced our understanding of the role and cellular pathways through which mTOR control cellular processes, such as translational initiation, actin organization, cell proliferation, and cell survival. mTOR is activated by phosphorylation and functions mainly through mTOR complex 1 or mTOR complex 2. mTORC1 is activated through tuberous sclerosis complex 1/2 dependent and independent mechanisms following the stimulation by growth factors, nutrient, amino acids, and other signaling pathways. The activity of mTOR is closely associated with cell proliferation and differentiation, apoptosis, and autophagy. Activation of mTOR prevents the induction of both apoptosis and autophagy through regulating its multiple targets. Given that the activity of mTOR has been involved in the pathogenesis of neurodegenerative disorders, cardiovascular abnormalities, metabolic diseases, renal transplantation, autoimmune abnormalities, and cancer, manipulating mTOR activation may represent as an innovative therapeutic strategy for these diseases. Yet, the role of mTOR in the body is complicated and therefore, its activity needs to be tightly regulated to achieve beneficial outcome in a specific pathological condition.