Aims and objectives: To determine the effect of OMW on seed germination and seedling growth of maize (Zea mays L). The study had following objectives: (1) To study the effect of different concentrations of OMW on seed germination and seedling growth of maize. (2) To determine the percentage phytotoxicity of OMW on maize. (3) To determine contents biochemical for both the endosperm and the embryo during germination. Olive Mill Wastewater (OMW) is considered as phytotoxic and thus an environmentally hazardous material, it is one of the most severe environmental factors that reduces and limits growth and development of plants. This study was conducted under laboratory conditions in order to evaluate the effect of OMW at three concentrations on seeds germination and seedling growth of maize (Zea mays L.). Seeds were soaked then placed in petri-dishes and irrigated with 1, 5 and 10% v/v concentrations of OMW. A control was moistened with distilled water. The germination percentage, root and shoot length, phytotoxicity percentage of root and shoot, and contents biochemical like total proteins, oil, total soluble sugars and starch for both the endosperm and the embryo of maize were observed. The results obtained showed beneficial effects using low concentrations of OMW whereas the treated plants with 1% of OMW showed a slight improvement in all the above growth parameters and contents biochemical, but the highest levels 5 and 10% of OMW had a negative effect compared with control.