The studied pond situated in Bangshal, old Dhaka of Bangladesh. To assess the water quality total of 14 parameters were regularly measured from the pond for 12 months (June 2010 to May 2011). The present, one year long study on the seasonality of phytoplankton and their relationship with some environmental factors in Bangshal pond reveals a total of 132 species of phytoplankton belonging to 6 different algal classes. Highest number of species was obtained from the class Chlorophyceae (40.15% of the total species). Dinophyceae (0.76%) represented least number of species (only one species) in the pond. The density of phytoplankton community ranged 5.23×106 ind/l to 0.77×106 ind/l. Phytoplankton chl a and its degraded product phaeopigment concentration ranged from 40.98-684.38 µg/l and 24.88-396.15 µg/l, respectively. Phytoplankton showed positive correlation with air temperature, alkalinity, dissolved oxygen (DO), soluble reactive phosphorus (SRP), soluble reactive silicate (SRS) and chlorophyll-a, total dissolved solids (TDS), conductivity, Phytoplankton showed negative correlation with water temperature, secchi depth, pH, nitrate-nitrogen (NO3-N) and phaeopigment.