Potential negative effects of exposure to Nigerian Qua Iboe Brent crude oil on the reproductive system of male rats was investigated. Forty Sprague-Dawley rats were used for the experiment. Exposure to Nigerian Qua Iboe Brent crude oil was achieved via oral administration of increasing doses (0.1, 0.2, and 0.4 ml/rat) every other day for 4 weeks. Cauda epididymal sperm reserves and relative weights of the testes as well as histological features of the testes of rats that received the crude oil treatment were compared to those of control rats. The results described here showed a significant (p < 0.01) dosedependent reduction in the cauda epididymal sperm reserves of rats that received crude oil treatment relative to the control group. The morphology of testes of the crude oil-exposed rats was characterized by the presence of interstitial exudates, degeneration, and necrosis of spermatogenic and interstitial (Leydig) cells. Findings indicate that exposure of male rats to Nigerian Qua Iboe Brent crude oil may have adversely affected their reproductive systems. This may imply possible reproductive health hazards for animals and humans that may be exposed to this environmental pollutant, especially in areas where oil spillage is a common feature.