The application of Pd/Fe3O4 nanoparticles (NPs) for the adsorption of sulfathiazole (STZ) from urine samples prior to high performance liquid chromatography-ultraviolet detection was studied. Pd/Fe3O4 NPs were synthesized using plant extract. Possible impact parameters in the extraction process such as magnetic adsorbents amount, extraction time, sample pH, and desorption conditions were investigated and optimized. Under the optimum conditions, the detection and quantification limits were 10 and 30 ng mL-1, respectively. The relative standard deviation for five measurements of 100 ng mL-1 of STZ was 5.8 %. The proposed method was used for the analysis of different urine samples, and acceptable recoveries in the range of 87.6 - 101.3% were obtained. These results indicated that biosynthesized Pd/Fe3O4 NPs can be used as an efficient adsorbent for extraction of sulfathiazole from urine samples.