Onychomycosis is a chronic fungal nail infection caused by several filamentous and yeast-like fungi, such as the genusCandidaspp., of great clinical importance. Black yeasts, such asExophiala dermatitidis, a closely relatedCandidaspp. species, also act as opportunistic pathogens. Fungi infectious diseases are affected by organisms organized in biofilm in onychomycosis, making treatment even more difficult. This study aimed to evaluate the in vitro susceptibility profile to propolis extract and the ability to form a simple and mixed biofilm of two yeasts isolated from the same onychomycosis infection. The yeasts isolated from a patient with onychomycosis were identified asCandida parapsilosis sensu strictoandExophiala dermatitidis. Both yeasts were able to form simple and mixed (in combination) biofilms. Notably,C. parapsilosisprevailed when presented in combination. The susceptibility profile of propolis extract showed action againstE. dermatitidisandC. parapsilosisin planktonic form, but when the yeasts were in mixed biofilm, we only observed action againstE. dermatitidis, until total eradication.