Candida albicans is present in oral health and has been linked with dental caries. So far, the behavior of the yeast in the presence of Streptococcus sanguinis has not been tested. The aim was to determine the effect of excess sugar as a cariogenic environment on the biological and physico-chemical parameters of single-species (C. albicans) and dual-species biofilms of C. albicans and S. sanguinis. An in vitro caries model was used. The biofilms were exposed to 10% sucrose or 0.9% NaCl for 5 min 3x/day/5 days. Viable cells, hyphal quantification, SEM, biofilm pH, H2O2 quantification and surface microhardness of enamel slabs were determined. Microbial viability and the number of hyphae were higher for sucrose exposure, in the dual-species biofilms induced by excess sugar and coexistence between the two microorganisms. Sucrose-exposed biofilms showed a progressive pH drop over the time course. H2O2 production was about 6 times higher for the dual-species biofilms. Enamel demineralization was higher in the single-species, suggesting an inhibitory effect due to S. sanguinis. Excess sugar increases the pathogenic potential of C. albicans biofilm. In dual-species biofilms, S. sanguinis prevents pronounced drops in pH, decreasing demineralization and stimulates the development of hyphae in the yeast.