Auxin is a plant growth hormone responsible for regulating growth, metabolism, apical dominance, and various other physiological processes of plants. The stress of heavy metal (HM) in plants is one of the main concerns nowadays. Excessive levels of HM in plants have severe negative effects on plants, such as a reduction in protein content and oxidative damage due to uncontrolled production of ROS as a result of HM toxicity. Auxin, a plant growth promoter, helps in mitigating negative effects of HM toxicity in plants. Auxin activates various genes or various enzymes responsible for conferring tolerance to plants under stress. Auxin promotes the stimulation of antioxidant machinery of plants, thereby restoring plant growth and development by relieving them from HM toxicity. The chapter discusses various biosynthesis pathways of auxin occurring in plants as well as the role of auxin involved in relieving plants from HM toxicity. The chapter discusses the effect of auxin on the antioxidant enzymatic machinery of plants so that the plants act against HM toxicity and develop tolerance to it.