BACKGROUND: Solanum nigrum is a widely used plant in oriental medicine where it is considered to be antioxidant, antiinflammatory and diuretic. This study aimed to evaluate the effect of Solanum Nigrum on uterine contractions. METHOD: Female Wistar Wister albino rats were used for the study. They were housed in a single large cage in an atmospheric controlled environment. Twenty-four hours before every experiment, 0.2 mg/kg of diethylstilbesterol constituted in 1:1 ethanol/water solution, was administered intraperitoneally as a pre-treatment to the rats to induce oestrus. It was done for two weeks during the study period. The phytochemical analysis was carried out to test for the phytochemical constituent of the plant. RESULT: The result showed that the extract inhibited the release of intracellular calcium ion. The effect of acetylcholine was significantly inhibited by the extract that is at 200mg/ml (p>0.05) and 300 mg/ml (p<0.01). The highest mean inhibitory effect of the extract observed on acetylcholine induced contractions was 90.54 ± 1.15. The oxytocin induced contraction was significantly inhibited by the extract at 200 mg/ml (p<0.05) and at 300 mg/ml (p<0.001) doses respectively. The highest mean inhibitory effect of the extract observed on Oxytocin induced contractions was 41.10±1.02 and was significantly stronger compared with acetylcholine induced contractions. CONCLUSION: The aqueous extract of Solanum nigrun inhibited the activity of oxytocin on the uterus, and it may possess relaxant activity.