Onychomycoses are diseases of fungal origin that affect the nail plate and have high rates of relapse and resistance to conventional antifungals. In addition to the impact on patient health, skin infections by fungi influence socioeconomic aspects, which, together with the resistance of the isolates, favor the development of strategies for obtaining new compounds with antifungal potential and of less expensive formulations. Hence, here we evaluated the therapeutic properties of cinnamaldehyde (CNM) alone and in combination with conventional antifungals against yeast isolated from infected nails. In addition, we tested the therapeutic effect of CNM on Tenebrio molitor larvae infected by Candida. Antifungal activity was analyzed using the broth microdilution assay and the fractional combination index (FIC) between CNM and antifungals by the checkerboard test. Anti-adhesion and antibiofilm activities were evaluated by colony-forming units counting method. CNM’s antimicrobial activity revealed MIC values ranged from 19.5 to 156 µg / mL and significantly reduced Candida’s adherence ability, biofilm formation and preformed biofilms. At sub-inhibitory concentration CNM was also capable of reducing Candida hyphae formation. CNM interacted synergistically with itraconazole (ITL) against C. parapsilosis and indifferent against Kodamaea ohmeri. Candida-infected larvae treated with CNM had a higher survival rate than those treated with ICL or fluconazole showing their high therapeutic potential. This study showed CNM’s antifungal and antivirulent activities and suggests the use of the compound, alone or in combination with antimycotics, as an alternative in the preparation of antifungal formulations.