In order to preserve the ecological quality of Aby lagoon, the aim of this study is to determine, according to seasons, spatiotemporal distribution and origin of phthaltes in the sediments of this lagoon. To do this, from September 2007 to July 2009, during seasonal sampling campaigns, sediment samples were collected at twenty (20) stations distributed along Aby lagoon. Analysis of the sediment samples, using gas chromatography-mass chromatography (GCMS- QP2010 plus), revealed presence of eight phthalates in the lagoon’s sediments. These are dibutyl phthalate (DBP), di (2-ethylhexyl) phthalate or bis (2-ethylhexyl) phthalate (DEHP), dimethyl glycol or di (2-methoxyethyl) phthalate (DMEP), phthalate di (2-methylpropyl) or diisobutyl (DIBP), dihexyl phthalate (DHP), di-isodecyl phthalate (DIDP), butyloctyl phthalate (BOP) and didecyl phthalate (DDcP). Areas of high population density as well as areas under the influence of the rivers that feed Aby lagoon contain more phthalates. However, the area under oceanic influence is free of phthalates. Statistical processing of data, using STATISTICA 7.1 and ADE-4 softwares, showed that the phthalates are continental and anthropogenic origin.