Abstract: Microbial content of sewage wastewater and the impact on microbial population of receiving surface water was studied in university of Ibadan, Oyo State, Nigeria. Sewage wastewater samples were collected over 3 months period and examined for microbial content at the University of Ibadan surface water receiving pre-treated wastewaters from staff residential quarters, academic departments and students hostels. Surface water samples that were contaminated as a result of the sewage discharge were collected and analyzed for microbial content as compared to samples without sewage contamination 10 m upstream section from the point of discharge (control). Some physico-chemical parameters of the water samples were also examined. The sewage wastewater samples were highly contaminated; sewage wastewater showed mean faecal coliform count of 2.4x10³ cfu/100 mL, mean total coliform count of 7.5x10⁵ cfu/100 mL and mean total aerobic count of 6.7x10⁷ cfu/100 mL. In the contaminated surface water sample, mean faecal coliform count (2.2x10² cfu/100 mL), total coliform count (3.1x10⁵ cfu/100 mL) and total aerobic count (8.2x10⁶ cfu/100 mL) are high compared to their respective values (1.1x10², 1.2x10⁵ and 6.3x10⁶ cfu/100 mL) for the control samples. These results were higher than Federal Environmental Protection Agency (FEPA) permissible limit of (500 cfu/100 mL). In this study, high microbial load in sewage wastewater with negative effects on microbial population in the receiving stream, further confirmed the need to pre-treat wastewater rather than discharging directly it to the environment.