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Interkingdom polymicrobial diseases are caused by different microorganisms that colonize the same niche, as in the case of yeast-bacteria coinfections. The latter are difficult to treat due the absence of any common therapeutic target for their elimination, both in animals and humans. <i>Staphylococcus pseudintermedius</i> and <i>Malassezia pachydermatis</i> belong to distinct kingdoms. They can colonize the same skin district or apparatus being the causative agents of fastidious pet animals’ pathologies. Here we analysed the antimicrobial properties of a panel of 11 peptides, derived from temporin L, against <i>Malassezia pachydermatis.</i> Only peptide <b>8</b> showed the best mycocidal activity at 6.25 μM. Prolonged application of peptide <b>8</b> did not cause <i>M. pachydermatis</i> drug-resistance. Peptide <b>8</b> was also able to inhibit the growth of <i>Staphylococcus pseudintermedius</i>, regardless of methicillin resistance, at 1.56 μM for methicillin-susceptible <i>S. pseudintermedius</i> (MSSP) and 6.25 μM for methicillin-resistant <i>S. pseudintermedius</i> (MRSP). Of interest, peptide <b>8</b> increased the susceptibility of MRSP to oxacillin. Oxacillin MIC value reduction was of about eight times when used in combination with peptide <b>8</b>. Finally, the compound affected the vitality of bacteria embedded in <i>S. pseudintermedius</i> biofilm. In conclusion, peptide <b>8</b> might represent a valid therapeutic alternative in the treatment of interkingdom polymicrobial infections, also in the presence of methicillin-resistant bacteria.