The influence of size and seasons on the bio-accumulation of some heavy metals in tissues of Clarias gariepinus from Qua Iboe River was studied for 6 months. A total of 64 samples of C. gariepinus were purchased alive from fishermen across 3 sampling stations, 32 apiece for dry and wet season. Samples were analyzed spectrophotometrically for heavy metals. Clarias gariepinus samples had a mean length of 38.911 ± 5.260 cm and a mean weight of 1454 ± 235.419 g. Mean metals concentrations in fish tissues were higher during dry season, except for cadmium (fish muscle). Lead was not detected in the tissues of Clarias gariepinus during both seasons. The muscles during both seasons were slightly polluted with Cu, Cr, Fe, Mn and Ni. Size affected all metal accumulation in Clarias gariepinus muscles except manganese, based on their relationship strength (r-values). Size of Clarias gariepinus influenced heavy metals pollution.