Reproduction and spawning patterns of the king fish (Scomberomorus commerson) were studied in the Persian Gulf (Hormozgan Province) and Oman Sea from Oct 2006 to Sep 2007. A total of 1120 fish was collected from different landing sites along the Iranian waters. Yearly analysis of the reproductive stages and gonadosomatic index showed a single reproductive cycle beginning in March and continued with a single spawning period from August to September. The mean length at first maturity (Lm 50%) for females was 83.6 Cm. The sex ratio was M: F= 0.97:1 which was not significantly (P> 0.05) different among samples (χ2 test). Isometric growth for this species was approved.