Another bacterium, identified as Staphylococcus warneri by matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), was obtained during the isolation of Staphylococcus aureus from yak milk by using Baird-Parker (BP) medium. The biochemical properties and antibiotic susceptibility of the Staphylococcus warneri strain were examined, and antibacterial experiments were carried out. Also, this study determined antibiotic residues in yak milk. The results showed that the biochemical properties of the obtained strain were consistent with those of Staphylococcus warneri. The strain was highly susceptible to most antibiotics except neomorphine, which had no inhibitory effect on it. Besides, all the yak milk samples were found to be negative for antibiotic residues. Although the opportunistic pathogen Staphylococcus warneri was detected in yak milk, it was sensitive to most antibiotics due to the pure environment of the milk source.