Microalgae is one of the live food of aquatic organisms in the aquatic ecosystem, and it is directly affected by pollution. In this study, Nannochloropsis spp. a brackishwater microalga, was subjected to different lead concentrations to determine its biological response in controlled conditions. It was cultured for four days in 10-L plastic carboys with 0 ppm (control), 0.5 ppm, 1 ppm lead concentrations with three replicates each arranged in a complete randomized design. Cell density and instantaneous growth rate were monitored daily, while Chlorophyll a and cell size were monitored before and after the experiment. After four days of culture, Nannochloropsis spp. at 0.5 and 1 ppm, Pb concentrations produced significantly (p0.05) in the initial and final cultures. Treatments with Pb concentrations had high chlorophyll a content compared with the control during the final sampling. The cell size of the microalgae was affected by lead (Pb) because it decreased after four days of culture. The results of this study showed that lead (Pb) affected the Nannochloropsis spp. However, it can still grow even in the presence of lead (Pb) pollutants.