Morphometric characters and reproductive biology were studied in S. officinalis collected at different seasons from the Iskenderun Bay, Turkey. A total of 2006 specimens (992 female, 1014 male) were sampled from September 2005 to August using a Mediterranean type deep trawl (22 mm mesh size). Mean mantle lengths for female and male were 9.83 +/- 1.66, 9.40 +/- 1.76 cm and the mean weights were 135.78 +/- 6.71g, 115.34 +/- 6.29g, respectively. Sexual maturity lengths were calculated as 12.04 for females and 10.30 cm for males. Mean diameter of eggs was measured as 5.367 +/- 9.12 mm per spawning period. Spermatophore lengths were estimated to range from 2.8 +/- 1.05 to 12.4 +/- 2.11mm. Population consisted of gonochoristic induviduals. Although, sex ratio of Sepia officinalis were not significantly different from the expected 1:1 ratio (p>0.05), a slightly male biased sex ratio was recorded.