The field study was applied in a clay loam soil in Al-Karamah (Al-Hamza Al-Sharqi, Diwaniyah Province) for the period October 1, 2022 to June 20, 2023. The aim of study was to evaluate the use of irrigation with treated wastewater on the Medicago Sativa during the summer and winter seasons. The results indicated a significant difference when using treated wastewater during the winter season compared to wastewater during the summer season. It was recorded a significant increase when the plants were exposed to irrigation with wastewater during the winter season for a period of not less than four months, as it gave the best results in the average vegetative and root characteristics. The average number and length of branches, number of leaves, root length, and weight of the fresh and dry vegetative and root group were 18.80 branches/plant, 60.40 cm, 144.63 leaves per branch, 34.08 cm, 72.92 g, 11.36 g, 65.37 g, 9.98 g, respectively, compared to wastewater during the summer season, which gave weak and thin plants that lacked the necessary nutrients for growth. The average vegetative and root characteristics of the plants were the lowest when irrigated with wastewater during the summer season. As for the estimation of the concentration of heavy metals including zinc, copper, cobalt, lead and cadmium in the plant, it did not reach the harmful limit according to the known standards of the Organization (FAO). The samples of the M. Sativa irrigated with wastewater during the summer season gave the highest significant increase in the concentration of heavy metals in this plant Zn, Cu, Co, Pb, as they reached 76.43, 62.31, 10.78, 10.78 µg/g dry weight respectively compared to the samples irrigated with wastewater during the winter season. It was also noted that the Cd metal did not have any significant effect in the M. Sativa plant samples irrigated with treated wastewater during the summer and winter seasons.