The effect of a tropical cyclone on the variation of phytoplankton biomass in terms of surface chlorophyll-a is brought out based on satellite observations and mixed layer model simulations in the Arabian Sea during 21 May--3 June 2001. Along the cyclone's passage, chlorophyll-a was high with extreme values (5--8 mg m-3) in the blooms of phytoplankton. The model simulations indicate deepening of mixed layer on the southeastern edge of the cyclone. This forced mixed layer deepening, due to intense wind stirring and cyclone-induced divergent geostrophic currents, has lead to the injection of nutrients into the surface layer, resulting in higher chlorophyll-a. This study suggests that the short-lived tropical cyclones would alter the generally prevailing oligotrophic (nutrient depleted) conditions into a productive surface layer in the Arabian Sea during spring intermonsoon.