This work describes the development of a method for analyzing pesticide residues in olive oil by GC-MS and HPLC-MS. Pesticides were separated from the oily matrix by size-exclusion chromatography. After extraction, 20 pesticides were separated and analyzed by GC-MS and 11 others HPLC-MS in electrospray mode. The development of this method enabled us to identify and quantify the pesticides of interest.