Baccaurea motleyana Müll. Arg. (Rambai), an Asian fruit belonging to the Phyllanthaceae family, is cultivated throughout Southeast Asia and has been traditionally utilized in folk medicine to address eye discomfort, digestive issues, insomnia, and fevers. This study of the peel employed four Kupchan fractions (PSF, DSF, ESF, and ASF) obtained from the methanol extract of the peel of B. motleyana for in vitro assessments, including antioxidant cytotoxicity and antimicrobial activities. The crude methanol extract was also used for in vivo evaluations, focusing on antidiarrheal and antidepressant effects, complemented by phytochemical screening and analysis using GC-MS/MS. The investigation of B. motleyana methanol peel extract identified 20 phytochemicals, with primary constituents, including phenol, 3,5-bis(1,1-dimethylethyl) (26.14%) and 1-heptadec-1-ynyl-cyclohexanol (23.12%). The extract exhibited potent antioxidant activity (IC