The aim of this study was to investigate the occurrence of the most common mycotoxins in commercial dry dog food using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Aflatoxin B1 (AFB1), aflatoxin G1 (AFG1), zearalenone (ZEN), deoxynivalenol (DON), T-2, beauvericin (BEA), citrinin (CIT), ochratoxin A (OTA), fumonisin B1 (FB1) were included in this study. The results showed that all these analytes could be found in the samples. Furthermore, only one sample was found free of mycotoxins contamination. All other samples (96.9%) were contaminated by at least three different types of mycotoxins. Among these mycotoxins, DON, ZEN, AFB1, FB1, CIT and BEA exhibited relatively high incidence, with occurrence rates of 78.1%, 62.5%, 87.5%, 93.8%, 68.8 and 96.9%, respectively. Furthermore, it is worth noting that AFB1 concentration in all AFB1 positive samples exceeded the maximum limits set by the European Union, with concentrations ranging from 30.3–242.7 µg/kg.