Studies were carried out from April 2016 to March 2017 for effective understanding of diversity combined with environment-influenced spatiotemporal dynamics of microfloral structure inKailash Khalwetland of Indian Sundarbans. A total of 36 phytoplankton genera were recorded from the study area. Eight major algal groups were in order of: Bacillariophyceae > Cyanophyceae > Chlorophyceae > Coscinodiscophyceae > Xanthophyceae > Euglenophyceae > Conjugatophyceae > Mediophyceae with respect to their quantitative abundance. Mean seasonal abundance was found highest in pre-monsoon (4.32 × 10³ cells l⁻¹) followed by post-monsoon (3.88 × 10³ cells l⁻¹) and monsoon (1.96 × 10³ cells l⁻¹). One-way ANOVA showed that seasonal difference in physicochemical parameters was statistically significant for temperature, DO, specific conductivity, TA, TS, Ca⁺⁺, nitrate, transparency, salinity, TH, turbidity, Mg⁺⁺and phosphate (p < 0.05). pH, temperature, total hardness, TDS nitrate, phosphate and silicate showed a close affinity with the distribution of phytoplankton community as evident from canonical correspondence analysis. Margalef richness index (3.121–3.774) and Shannon–Wiener diversity index (2.730–2.939) indicated moderately rich phytoplankton diversity in the wetland ecosystem.