Purpose: The purpose of this study was to investigate the effects of polyphenol-rich cranberry extracts on dual-species Streptococcus mutans-Candida. albicans biofilms implicated in contributing to the severity of early childhood caries. Methods: S. mutans-C. albicans biofilms were grown on saliva-coated hydroxyapatite discs (s-HA) mounted on the high-throughput Amsterdam Active Attachment model. The s-HA discs were treated with the cranberry extracts/vehicle control for five minutes just before biofilm growth and subsequently, for similar exposure times, after 12 hours and 24 hours of biofilm growth. The treated 24-hour-old biofilms were then assessed for acidogenicity, metabolic activity, exopolysaccharide (EPS)/microbial biovolumes, structural organization, and colony forming unit (CFU) counts. Results: Treatment with 500 to 1,000 μg/mL of the cranberry extracts produced significant reductions in acidogenicity and metabolic activity (PS. mutans-C. albicans dual-species biofilms in an in vitro model.