The study was carried out to determine the phytochemical content, antioxidant and antidiarrhoeal activity of methanol extract of whole plant of Limnophila repens. The total phenolic, flavonoids, flavonols, tannins, β-carotene, lycopene, chlorophyll-α, and chlorophyll-β contents were found to be 65.21±0.004 mg GAE/g, 44.83±0.003mg QE/g, 17.21±0.002mg QE/g, 56.27±0.002 mg GAE/g, 1.32 ± 0.01μg/g, 0.93±0.012μg/g, 11.85±0.04mg/g and 9.69±0.037 mg/g, respectively. In vitro antioxidant potential of L. repens was assessed using various methods including 2,2-diphenyl-1 picrylhydrazyl (DPPH), hydroxyl radical scavenging assay, reducing power assay, FRAP assay and thiobarbituric acid assay. IC50 values of the aforesaid tests were found 2.33mg/mL, 442.31μg/mL, 374μg/mL, 55.09μg/mL, and 4.30mg/mL, respectively. The total antioxidant capacity was observed 140.7±0.004mg/g AAE. Castor oil induced diarrhoea method was conducted to investigate the antidiarrhoeal activity of L. repens. At the dose of 400mg/kg BW, the plant extract (35.62% inhibition of diarrhea) exhibited stronger effect compared to standard drug, loperamide (27.4% inhibition of diarrhea). [ABSTRACT FROM AUTHOR]