This study was carried out to determine some aspects of reproductive biology of king soldier bream, Argyrops spinifer ( Forsskål 1775), Family: Sparidae in Iraqi marine waters, Northwest Arabian Gulf. Samples were monthly  collected from October  2013 to May 2014 by trawl nets. Variations in gonado–somatic index (GSI) were recorded. It was found that variations in hepato–somatic index (HSI) were related to feeding activity rather than gonadal maturation. Peaks of HIS and GSI were recorded at same period. Six maturity stages were defined for male and female of king soldier bream fish: immature, quiescent, maturing, mature, ripe and spent. Histological examination showed six stages of oocytes for females in this fish: chromatin nucleolus oocytes, perinucleolus oocytes, yolk vesicles, vitellogenic oocytes, hydrated oocytes, atretic oocytes. Five stages for males including: spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa .The gonado-somatic index for males and females reached their peak at ripe stage (2.165) and (3.789) respectively. The peak of hepato-somatic index was in immature stage in males (1.260) and in females (2.409).