Oral biofilms are complex microbial communities involved in the development of dental caries and periodontal disease. Limitations associated with conventional antiseptics have stimulated interest in plant-derived antimicrobial compounds. Essential oils (EOs) and their major constituents may affect bacterial viability, adhesion, biofilm formation, membrane integrity, and virulence-associated processes. This narrative review comparatively examines eugenol, carvacrol, thymol, and menthol, representing major constituents of clove, oregano/thyme, and peppermint oils, respectively. Particular attention is given to their antimicrobial and antibiofilm mechanisms, effects on biofilm development, and potential influence on oral microbial homeostasis. Eugenol, carvacrol, and thymol have relatively well-supported antimicrobial and antibiofilm effects, whereas evidence for isolated menthol remains more limited. Importantly, the activity of complete EOs depends on their chemical composition and interactions among constituents and cannot be inferred solely from the activity of individual compounds. Current limitations include chemical variability, formulation challenges, potential cytotoxicity, and predominance of in vitro evidence. Further research using standardized multispecies oral biofilms and well-designed clinical studies is needed to clarify the potential role of EOs in oral biofilm management.