Dangana Lake was constructed primarily to provide water for drinking, domestic activities and control flood. Phytoplankton assemblage and physicochemical parameters of Dangana Lake, Lapai, Niger State Nigeria were investigated monthly between March and October 2019 using standard methods and procedures. Water samples were collected from 3 different stations in the Lake. The result of the lake shows water temperature (23.2-29.5ºC), Biochemical oxygen Demand (2.30-3.91mg/l), Dissolved oxygen (3.40-4.70mg/l), water pH (6.10-7.5), Electrical conductivity (60.00-121µS/cm), Nitrates (0.30-1.05mg/l) and Phosphate (0.53-1.75mg/l). Temperature, DO, BOD5, and pH shows no significant difference (p>0.05) among sampling sites, however, Electrical conductivity, Nitrate and Phosphate differs significantly among sampling sites (p<0.05). Seasonally there was a significant difference (p<0.05) among sampling months in all the physicochemical parameter measures. A total of Seventeen (17) species of phytoplankton in six (6) families were encountered. The percentage abundant of phytoplankton revealed Bacillariophyta (36.84%), Dinophyta (33.38%), Chlorophyta (17.05%), Heterokontophyta (6.93%) Cyanophyta, (4.76%), and Euglenophyta (1.02%). Phytoplankton population was significantly higher during the dry season than in the raining season. The Canonical Correspondence analysis (CCA) correlated positively between the measured physicochemical parameters and the observed organisms. The nutrient status of the lake shows a medium range as indicated by the measured environmental parameters.