<p>Biological treatment is one of the most preferable strategies to complete and safe removal of pollutants. Pyrene (PY) is the first member of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) that represents various concerns to biological life and human health. In this study, two different algal strains exhibited different capability to degrade PY along 30 days of incubation in the light. Dry weight, total chlorophyll, and carotenoids were growth parameters that were determined to detect robust of two algal strains to get used of PY as a source of carbon. Oscillatoria sp. could degrade 95% while Chlorella sp. could degrade 78.71 % of PY (50 mg/L) after 30 days of incubation. Both algal strains could completely remove 10 and 30 mg/L of PY. On the other hand, the degradation capability of Oscillatoria sp. was significantly exceeded than Chlorella sp. under the same incubation condition and at (50 and 100 mg/L) of PY.</p>