Environmental stresses are one of the most important reducing factor for plant’s growth and productivity worldwide. Among them, salinity and drought are known as the most harmful. Reactive oxygen species (ROS) production is a frequent consequence of most stresses, including salinity and drought. These free radicals cause serious damages to plant’s structure by oxidizing membrane lipids, proteins and nucleic acids. During the evolution process, plants acquire an antioxidative system consisting of nonenzymatic antioxidants, such as β-carotenes, ascorbic acid (AA), α-tocopherol (α-toc), and antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POX). Considering the fact that ROS production is an outcome of plant metabolism, controlling the ROS levels is highly vital for plant cells survive. There are considerable numbers of scientific researches regards to the antioxidative responses of plants grown under drought and salinity. These responses highly depend on plant species, other environmental conditions, growth stage and other factors. In this review, the biochemistry of enzymatic and non-enzymatic antioxidants and plant’s antioxidative system changes in response to drought and salinity were expansively evaluated. DOI: http://dx.doi.org/10.3126/ijls.v9i2.12042 International Journal of Life Sciences 9 (2) : 2015; 1 - 8