To evaluate the safety of food for pets, the migration of chemical substances from pet tableware was investigated by mass spectrometry. The presence of polymer additives Irgafos 168 and Erucamide were suspected based on mass spectra and were confirmed to be present in polypropylene tableware. The amount of substances migrated using simulated saliva was examined by liquid chromatography-mass spectrometry after solid phase extraction and purification. Photoionization was found to be suitable for the simultaneous determination of these substances. The detection limits of the established method were 0.019 μg/mL for Irgafos 168 and 0.022 μg/mL for Erucamide. Five different types of pet tableware purchased in local markets were examined and no analytes were detected in the simulated saliva using shaking extraction. In this study, the risk to pets from the substances migrated from pet tableware was considered to be sufficiently low.