In this work, we investigate the suitability of a commercial available and low cost polyethersufone (PES) sorbent for the microextraction of 1H-benzotriazole (BTri), and four polar derivatives (4 and 5-methyl-1H-benzotriazole, 4-TTri and 5-TTri; 5,6-dimethyl-1H benzotriazole, XTri; and 5-chloro-1H-benzotriazole, 5-ClBTri) from surface and wastewater samples. The performance of liquid chromatography (LC) combined with quadrupole time-of-flight mass spectrometry (QTOF-MS) for the selective determination of target compounds is also discussed. Parameters affecting the efficiency of the microextraction step, such as sample’s pH, ionic strength, stirring speed and extraction lapse of time, and the PES membrane desorption process have been thoroughly investigated. Analytes were extracted from 15 mL samples, containing a 30% of sodium chloride and adjusted at pH 4.5, using a tubular PES sorbent (5 cm length x 0.7 mm o.d., sorbent volume 42 μL). After methanol desorption and solvent exchange, benzotriazoles were determined by LC-MS, with chromatograms extracted using a mass window of 20 ppm, centered in their [M+H]+ ions. The identity of chromatographic peaks was confirmed with accurate ion product scan (MS/MS) spectra. The method provided limits of quantification (LOQs) between 0.005 and 0.1 ng mL-1, and relative recoveries from 81% to 124% (except for XTri in sewage samples, ca. 60%) with associated standard deviations between 2% and 9%. The efficiency of the PES sorbent for the extraction of these compounds has been compared with that attained by stir-bar sorptive extraction (SBSE), with polydimethylsiloxane (PDMS) covered stir bars. The PES polymer achieved significant higher responses (5- to 20-fold) for these polar pollutants. To the best of our knowledge, this research constitutes the first application of both techniques (microextraction using a PES sorbent and LC-QTOF-MS) for benzotriazoles determination in water samples. The method was used to provide data regarding the levels of target compounds in river and urban wastewater samples, including the individual quantification of 4-methyl and 5-methyl-benzotriazole isomers. Obtained results confirmed the ubiquity of benzotriazole, 4-methyl and 5-methyl-benzotriazole in urban wastewater and their incomplete removal at sewage treatment plants