Abstract A simple and sensitive method using magnetic solid phase extraction (MSPE) followed by spectrofluorimetric detection has been developed for separation and determination of aflatoxin M1 (AFM1) in liquid milk. The method is based on the extraction of AFM1 on the modified magnetic nanoparticles (MMNPs) and subsequent derivatization of extracted AFM1 to AFM1 hemi-acetal derivative (AFM2a) by reaction with trifluoroacetic acid (TFA) for spectrofluorimetric detection. Magnetic nanoparticles (MNPs) coated by 3-(trimethoxysilyl)-1-propantiol (TMSPT) and modified with 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) were used as adsorbent in MSPE procedure. Influential parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions the calibration curve for AFM1 determination showed good linearity in the range 0.030–10.0μgL−1 (R2=0.9991). The repeatability and reproducibility (RSD%) for 0.050μgL−1 of AFM1 were 4.5% and 5.3%, respectively and limit of detection limit (S/N=3) was estimated to be 0.010μgL−1. The developed method was successfully applied for extraction of AFM1 from spiked liquid milk and natural contaminated liquid milk. The good spiked recoveries ranging from 91.6% to 96.1% were obtained. The results demonstrated that the developed method is simple, inexpensive, accurate and remarkably free from interference effects.