A thin film microextraction method using elecrospun magnetic polybutylene terephthalate nanofibers is developed and implemented to isolate some selected triazines. Due to the high mechanical stability of these nanofibers, they are repeatedly used under harsh magnetic stirring and ultrasonic conditions without any damage and structure degradation. The presence of magnetic nanoparticles within the nanofiber structure increases the extraction efficiency while the fibers could be collected by an external magnet. The synthesized nanocomposite showed strong affinity toward the selected analytes. Apart from the concentration of magnetic nanoparticles within the nanocomposite network, the effect of different parameters on the extraction and desorption processes including the sample pH, extraction time, sample volume, type of desorption solvent, solvent volume, and desorption time were optimized. Eventually, the detection limits were in the range of 0.02-0.05 ng/mL, while the limits of quantification were between 0.1 and 0.2 ng/mL. The linear dynamic range was 0.1-100 ng/mL, and the relative standard deviations were 4-9% (n = 3). The developed method was extended to the real water samples, and the relative recoveries were in the range of 86-103%, indicating that the prepared sorbent is suitable for extraction of triazines from environmental samples.