Introduction: The results are presented of the inter-laboratory validation of a liquid chromatography–tandem mass spectrometry method for the determination of eight mycotoxins (aflatoxin B1, deoxynivalenol, fumonisin B1, fumonisin B2, ochratoxin A, toxin T-2, toxin HT-2 and zearalenone) in animal feeds. Material and Methods: This study was an essential part of the method’s transfer from the National Reference Laboratory to six regional laboratories in Poland working in the official survey of mycotoxins in feed. The laboratories received a batch of standard solutions, blank samples and quality control materials on which to perform analysis with one procedure and different liquid chromatography–tandem mass spectrometry conditions. Results: The validation results show good precision (reproducibility coefficient of variation 3.7–20.5%) and accuracy of the method (recovery 89–120% and trueness 94–103%) and sufficient skills of the laboratory personnel. Conclusion: The study is an example of the successful transfer of the method among laboratories