Abstract: Leaf extracts of Parquetina nigrescens (AAfz.) Bullock, a plant commonly employed for the treatment of gastro-intestinal disorders in Nigeria was tested for antimicrobial activity and gastro-intestinal protective effect. Aqueous leaf extract showed antimicrobial activity against a range of bacteria in the following order of activity: Staphylococcus aureus > Salmonella typhi > Proteus mirabilis > Pseudomonas aeruginosa > Bacillus subtilis > Proteus vulgaris, whereas the ethanol extract was effective only against Pseudomonas aeruginosa and Salmonella typhi. The aqueous extract also significantly reduced gastric acid secretion, reduced ethanol-induced gastric ulceration (p<0.05) and caused elevation in gastric mucus secretion. The antimicrobial activity against the common pathogenic microbes S. aureus, S. typhi and P. aeruginosa may account for its acclaimed potency against diarrhea. In addition, its protective effect against oral administration of absolute ethanol reflected by the increased mucus secretion and decreased gastric acid secretion may also be responsible for its claim as having anti-ulcer property.