Physico-chemical parameters of Kenyir Lake at Como region were measured to assess the health of the ecosystem. Although the difference in air temperature was 27%, the surface water showed 2.5% variation within 24 hours. The fluctuations of water temperature (30.4-31.7°C) at depths of 3 and 6 m were 3.5 and 2.2% respectively within 48 hours. The pH values until 6 m depth ranged from 6.7-7.2. In a similar manner, the dissolved oxygen (DO) at the surface and 3 and 6 m depths were within the range of 8.5-10.3 mg/1 during 48 hours. Fluctuations of total dissolved solids were only 4 to 5.5% whereas chlorophyll a was 0.0075 pg/1 (2400 hrs) and 0.1038 pg/1 (1800 hrs) with 93.7% fluctuation. The hydrogen sulphide (H7S), nitrate (NO3) and phosphate (PO4) contents were always below the detectable range in the surface water whereas at 3 m, these values were; 1.0-1.6 pg/1 (H2S), 0.26-0.50 pg/1 (NO,) and 0.01-0.09 pg/1 (PO4) and at 6 m the values were 1.0-3.6 pg/1 (H7S), 0.20-0.40 pg/1 (NO3) and 0.02-2.30 pg/1 (PO4). Considering the optimal values of DO, pH and other chemical parameters in Kenyir Lake, it has been presumed that the reason for mass mortality and slow growth of the fish cultured in cages could be related to high temperature regime (>30°C).