Carvacrol is an important component of essential oils and recently has attracted much attention as a result of its biological properties, such as a wide spectrum of antimicrobial activity. The aim of this study was to evaluate the effect of carvacrol in liquid and vapour phase on preformed biofilms of Staphylococcus aureus and Staphylococcus epidermidis by determining biofilm biomass and cultivable cell numbers, and by using epifluorescence and scanning electron microscopy. Carvacrol was able to reduce biofilm biomass and cell viability more effectively when used with liquid contact rather than with vapour phase. The efficacy of treatment with carvacrol vapour was found to be dependent on exposure time. The predominance of red fluorescence using a LIVE/DEAD BacLight Viability kit (Molecular Probes) and the partially destroyed biofilm architecture as determined by microscopy in treated samples provided evidence for the efficacy of carvacrol. The findings of this investigation suggest a potential application for carvacrol in the inactivation of staphylococcal biofilms.