The aim of this study was to investigate the effect of Archachatina marginata mucin on the aggressive factors of gastric ulcer challenged rat stomach tissue. Thirty adult male wistar rats were divided into six groups of five rats each. Group I (normal control) was administered with 2 ml/kg b.w distilled water; Group II was administered with 120 mg/kg b.w indomethacin only. However, Groups III, IV and V were administered with 200, 400 and 800 mg/kg b.w mucin respectively, while Group VI was administered with the standard drug (mistoprostol) daily for 10 days. After the 10th day of pretreatment, Groups III-VI were administered with 120 mg/kg b.w indomethacin. Gastric juice was collected, after animals had been anaesthetized. The rats were sacrificed by cervical dislocation seven hours after indomethacin administration. Free acidity, total acidity, pepsin activity, gastric juice volume and acid output were determined using standard methods. There was a significant increase in the level of free and total acidy as well as pepsin activity with a concomitant increase in gastric juice volume as well as acid output (59.00±5.43 mEq/L), (85.20±7.49mEq/L), (1.39±0.62μg/ml), (4.40±0.77ml) and (0.26±0.04 μEq/L/4hrs) in Group II compared to Group I (normal control) (40.60±6.39mEq/L), (71.00±9.30mEq/L), (1.18±0.41μg/ml), (2.58±0.87 ml) and (0.11±0.03μEq/L/4hrs) respectively. However, there was a significant reduction in the level of free and total acidity as well as pepsin activity with a concomitant decrease in gastric juice volume and acid output in Groups III, IV and V administered with 200, 400 and 800 mg/kg b.w. While values recorded with 800 mg/kg b.w mucin was not significantly different from those obtained with the 20 μg/kg b.w standard drug (mistoprostol). In conclusion, It can be deduced from this work that mucin from A. marginata can be considered suitable candidate for the development of a gastric ulcer drug.