Zinc (Zn) is the next most widespread transition heavy metal following iron (Fe) and a necessary micronutrient implicated in diverse physiological and biochemical processes in plants. However, Zn accessibility to plants is hindered by its immobile behavior and hostile soil conditions, leading to its deficit despite being high quantities present in soil. Nowadays, Zn insufficiency is the most prevalent micronutrient scarcity in plants, humans, and animals, with 25–30% of global population being affected by it. Shortage of Zn leads to loss in yield and in severe cases even death of plant. Nevertheless, simultaneously, problem of Zn toxicity exists in few areas largely because of environmental contamination derived from farming and industrial activities. Excess Zn causes initiation of oxidative burst and obstructs several plant metabolic processes that cause cellular alterations. Physiological, biochemical, and molecular mechanisms that permit plants to flourish in Zn deficit and polluted soils are inadequately explored and comprehend. Thus, this chapter intends to review and discuss the various features of different morpho-physiological, biochemical, and molecular responses in plants raised under Zn deficit as well as toxic conditions to understand how plants respond differentially in two extreme Zn conditions.