This work reports a fast and reliable analytical method for the screening of priority pesticides (PPs) in Ulva sp. seaweeds by gas chromatography with electron capture detection. Extraction and sample clean-up were performed in one single step by selective pressurized liquid extraction (SPLE). Several parameters affecting SPLE performance were optimized. Method performance was compared with standard Soxhlet extraction. Significant decrease of the time of analysis with better recoveries for a greater number of PPs was achieved by SPLE. Average recoveries ranged from 71 to 103% with RSD < 10%. Field application showed the presence of PP in the range of 3-11 ng g(-1) in seaweeds collected in a coastal lagoon after a long period of heavy rains. These results suggest that Ulva sp. seaweeds tend to accumulate PPs and have the potential to be used as early alert signals of aquatic pollution especially after rains and storm events.