This study determined the bacteriological quality of water from the Opa River and assessed the impact of human behaviour on the quality of water along the river course. Twenty five water samples were collected over a period of five weeks at five selected points based on population clusters along the river. A hundred questionnaire items were administered to randomly selected residents to elicit information about the water body and predominant communal behaviours. Water samples were analyzed by standard microbial techniques and isolates were identified. The isolates obtained were tested for their resistance to antibiotics via standard methods. Descriptive statistical techniques were used to obtain the minimum and maximum values of Total Heterotrophic Bacterial (THB) count and Total Coliform Bacterial (TCB) count. The analysis of variance (ANOVA) test was used to compare the means. Heterotrophic bacteria load at the five sampling points ranged between 2 x 10 6 and 13 x10 6 cfu/ml while the most probable number of coliforms in 100 ml of samples was between 34 and 1600. The organisms isolated from the samples included those of the Genera Citrobacter Enterobacter Escherichia, Proteus, Klebsiella, Salmonella, Serratia, Yersinia, Shigella, Pseudomonas and Vibrio. Escherichia coli had the highest percentage frequency of occurrence (23.73%) and was isolated at all sampling points. In all areas, communal behaviour towards the river was generally poor. Some respondents reported symptoms associated with water borne illnesses which included vomiting (28.5%), passing out of watery stool (57.2%) and headache and dizziness (14.3%). The Opa River was found to be mostly contaminated by multiple antibiotic resistant organisms. Opa River could be a source of potential pathogens associated with water borne diseases and could consequently; serve as a pathway for human contamination, most especially of dwellers located along its banks that depend on Opa River water.