Growth and yield enhancement by the insecticide TrimaxTM (active ingredient: imidacloprid) in cotton (Gossypium hirsutum L.) has been reported in the absence of insect pests, but research documenting this is lacking. The unique molecular structure of imidacloprid may lessen the adverse effects of environmental stress. The effect of Trimax on the growth and yield of cotton was evaluated with field and growth chamber studies. Trimax-treated plants were shown to grow more vigorously, mature earlier, and produce more lint yield than untreated control plants. Increased carbohydrates and dry matter production of Trimax-treated plants were attributed to enhanced plant metabolism after Trimax application, which was recorded as improved photosynthesis, decreased chlorophyll fluorescence and lower membrane leakage. Antioxidant enzyme activity measured after foliar applications of Trimax was increased in untreated compared to treated plants, indicating that treated plants suffered less from stress. This research suggests that the imidacloprid molecule possibly has antioxidant properties, enabling plants to better tolerate environmental stress. This is the first research documentation of the growth promoting properties of Trimax and the mode of action of yield enhancement.