Abstract: Pistia stratiotes (Araceae) is a Bangladeshi medicinal plant used traditionally to treat a various diseases. The present study was designed to investigate of antinociceptive and antidiarrhoeal activity of methanolic extract of the leaves of Pistia stratiotes. The extract produced significant writhing inhibition in acetic acid-induced writhing in mice at the oral dose of 250 and 500 mg kg-1 body weight (p<0.001) comparable to the standard drug diclofenac sodium at the dose of 25 mg kg-1 of body weight. The extract showed antidiarrhoeal activity on castor oil induced diarrhoea in mice, it increased mean latent period and decreased the frequency of defecation significantly at the oral dose of 250 and 500 mg kg-1 body weight (p<0.01) comparable to the standard drug Loperamide at the dose of 50 mg kg-1 of body weight. The obtained results provide a support for the use of this plant in traditional medicine and its further investigation.