The spawning seasons of Sardinella longiceps of Indian oil sardine was investigated based on examining gonads along the area of Oman Sea, Muscat, Sultanate of Oman. The length at first maturity (L50%) and Gonado-somatic index (GSI) of females were considered. Length at first maturity was estimated as 182 mm (TL). The GSI shows two spawning seasons: the minor one from December to March and the major once from June to September. The maximum GSI at-tained between 5.0 and 5.2 during June and September respectively, suggesting a spawning peak occurred during that period.