Water quality profile of Pergau Reservoir or also known as Sultan Ismail Petra Hydroelectric Reservoir has been conducted from 28th October to 3rd November 2019 during Pergau scientific expedation 2019. Three (3) lentic sampling stations (P1, P2 and P3) were selected with eleven (11) water parameters such as water temperature, pH, biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), total dissolved solid (TDS), dissolved oxygen (DO), turbidity, ammonical-nitrogen, oil and grease (O&G), and total coliform were analyzed for water quality status of Pergau Lake. Stratification profile of DO, pH and water temperature were recorded by 10m depth at all lentic stations. Generally DO, temperature and pH reading at the surface lentic sampling stations ranging between 7.11 to 9.21 mg/L, 27 to 27.5 °C and 7.50 to 8.72, respectively. Anoxic layer was detected at depth of 9 m at P1 whereas 3 m at P2 and P3. Profiling of DO, pH and water temperature shown decreased pattern when the water depth increased. Others parameters such as COD at the subsurface were ranged from 1.3 to 1.4 mg/L, TSS reading recorded ranged from 4.00 to 6.80 mg/L, ammoniacal-nitrogen ranged from 0.05 to 0.07 mg/L whereas BOD5 were ranged from 1.3 to 1.4 mg/L. The Department of Environment – Water Quality Index (DOE-WQI) classification was used to assess the water quality status of the selected sampling locations. The results showed that all locations fall under Class I ranged between 92.66 to 94.55% and in summary the area can be classified as clean and suitable for sensitive aquatic organisms.