According to the data of Global Burden Disease in 2016, periodontal disease is the 11th disease suffered by 750,487 people worldwide. Gingivitis occurs due to dental plaque formation. A half of bacterial plaque populations are Streptococcus sp. Streptococcus sanguinis is a predominant bacterial that initiates plaque formation. The adherence of this bacteria is mediated by fimbriae, pilus protein, lipoprotein, and glucosyltransferase enzymes. Hibiscus flower has a potential as an antimicrobial agent that may inhibit plaque formation due its active component i.e. flavonoid, tannins, and saponin. This study aimed to investigate the effect of Hibiscus rosa-sinensis L. flower extract concentration on the growth of Streptococcus sanguinis. Wells diffusion method was used in this study, using 100 μl bacterial suspension of 1,5 x 108 CFU/ml of bacteria. Hibiscus flower extract (2%, 4%, 6%), chlorhexidine 0,12% as a positive control, and distilled water as a negative control were added in the agar wells. The results showed that all concentrations (2 %, 4%, 6 %) of Hibiscus flower extract higher significantly compared to negative control. The concentration of 4% and 6% are higher ;significantly compared to positive control. The largest inhibitory zone was at a concentration of 6% (6,35±0,09 mm) and the smallest inhibitory zone was at a concentration of 2% (2,51±0,12 mm). The conclusion is that the concentration of Hibiscus rosa-sinensis L. flower extract affects the growth of Streptococcus sanguinis.