The aim of study was to determine effects of nickel chloride on the physiology of Lemna minor through used three different concentrations of nickel chloride (10, 20, 30 ppm) for a month in order to measure the amount of total chlorophyll and its protein content. The results of the investigation showed that exposure to nickel chloride causes several effects on the physiology of Lemna minor through reduced biomass, slowed leaf growth at high nickel concentrations, decreased protein levels, reduced chlorophyll content, and impaired photosynthesis. It also causes oxidative stress by increasing MDA levels, altering antioxidant enzyme activity, and affecting nickel uptake from water. However, high levels of nickel are toxic. Symptoms of nickel-induced stress include yellowing of leaves, tissue death, and metabolic disturbances.