The decoction (D) of the bark of Ficus racemosa Linn (Family: Moraceae) is claimed as an antidiuretic by some Sri Lankan traditional practitioners. However, the validity of this claim has not been scientifically proven or refuted. The aim of this study was to evaluate the antidiuretic potential of D of the bark of F. racemosa (made as specified in traditional use) in rats using three doses (250, 500 or 1000 mg/kg) following oral administration. The reference drug used was ADH. The results demonstrated both the low- and high-doses of D and ADH significantly impaired the total urine output. The D-induced antidiuresis had a rapid onset (within 1 h), peaked at 3 h and lasted throughout the study period (5 h). However, antidiuretic potential of D was about 50% lower than that of ADH. The D was well tolerated even with subchronic administration. The D caused a reduction in urinary Na+ level and Na+/K+ ratio, and an increase in urinary osmolarity indicating multiple mechanisms of action. The results provide scientific support for its claimed antidiuretic action and deserve intensive scrutiny.