This study was undertaken to examine the extent of agricultural chlorinated pesticides in edible red seaweeds viz. Gracilaria verrucosa and Gelidiella acerosa, collected from four sites of Gulf of Mannar analysed from September 2017 to January 2018 for OCP residues using GC-MS as per AOAC 2007.01 QuEChERS extraction method. The total OCPs concentration in Gelidiella acerosa ranged between 6 ngg-1 and 508 ngg-1 and in Gracilaria verrucosa between 0.36 ngg-1 and 270.41 ngg-1. In Gelidiella acerosa, OCP concentration was high in those collected from Rameswaram and in Gracilaria verrucosa, from Seeniyappa Dhargah. The OCP concentration was recorded high in January, due to the fruiting period of seaweeds. The three major OCPs recorded were ∑ HCH, endosulfan and endrin. Specific accumulation of more endrin residues by Gelidiella acerosa is a distinct feature observed in this study. In Gelidiella acerosa, endrin accumulation was quite dangerous as its concentration was 30 ng g-1, above the MRL of 10 ng g-1. The HCH and endosulfan were also above the MRL of 10 ng g-1 and 50 ng g-1 in 50% of both the seaweed samples. The alarming level of endosulfan and endrin in Gelidiella acerosa is an indication of their persistence in the environment. Suitable remedial measures to save the marine ecosystem as well as edible food resource is the need of the hour.