Two pot experiments were carried out to investigate effect of deficit irrigation with wastewater on seed yield, heavy metals and seedling emergence in oat (Avena sativa). The research at seedling stage included different ratios of sewage-contaminated water (100% well water, 75% well water + 25% wastewater, 50% well water + 50% wastewater, 25% well water + 75% wastewater and 100% wastewater) and three irrigation intervals (1, 2 and 3 days). The research at complete plant stage included different ratios of sewage-contaminated water used at seedling stage and irrigation intervals of 2, 3 and 4 days. Results showed that at oat seedling stage, irrigation interval of 1 days and 100% wastewater produced the highest seedling weight. Irrigation interval of 3 days with 100% wastewater had the lowest seedling emergence. At complete plant stage, by increasing wastewater concentration, leaf chlorophyll content was increased, but relative water content was decreased. 100% wastewater produced the highest seed yield, 1000-seed weight, concentrations of zinc, copper and potassium. According to references, the concentration of studied heavy metals was lower than dangerous threshold.