Domestic and industrial wastes of Dhaka City discharged into the river Buriganga by four main discharge pathways. Among Pagla sewage treatment plant (PSTP) outfall is one of them. The studied lagoons of PSTP is one of those related stations from where the present data were collected. To assess the water quality at the treatment plant concerned, a total of 15 parameters were regularly measured from the two lagoons for 10 months. The phytoplankton diversity in the lagoons is represented by 6 algal classes under which a total of 127 species were recorded. At the two lagoons of Pagla itself, a total of 46 and 54 genera were recorded L-1 and L-2, respectively and a total of 10 genera were recorded from another part of treatment plant (separator). Highest number of species was obtained from the class Chlorophyceae (41.39% of the total species). Data on limnological variables recorded during the present investigation showed an almost clear picture about the water quality of the lagoons of Pagla.