Phytotoxicity is defined as the detrimental effects of chemical products used for pest eliminating or growth regulating purposes on some morphological, anatomical and physiological processes of plants. We examined the effects of pyriproxyfen, which is used to protect crops against whitefly, to determine whether it adversely affects maize plants. For this purpose, maize (Zea mays L. saccharata Sturt.) seeds were treated with several pyriproxyfen concentrations (0.0, 0.1, 0.2, 0.4, and 0.6 ppm) for 72 h under controlled conditions. The results showed that, while low concentrations of the insecticide had little effect on the growth of maize seedlings, increasing the concentration gradually had harmful effects on the growth. The highest insecticide concentration led to a remarkable decrease in all the growth parameters of maize seedlings. It was found that maize growth was significantly inhibited by increasing the concentration of pyriproxyfen, which adversely affected seed germination and seedling growth. Stomata index decreased in both adaxial and abaxial surfaces of leaves treated with increasing concentrations compared with the control group. The adaxial surfaces of maize leaves always had fewer stomata than the abaxial surfaces. As insecticide concentration increased, photosynthetic pigment contents decreased except for anthocyanin, but the proline accumulation increased as an adaptation to toxic treatment. This work suggests that excessive and uncontrolled usage of pesticide pyriproxyfen results in phytotoxic effects by inducing some morphological, anatomical, physiological and metabolic processes. In addition, as chemical compounds accumulate, pyriproxyfen is thought to adversely affect all living beings feeding on plants that are exposed to chemicals, and also negatively affects the environmental factors such as, soil, air and water.