B ackground: Streptococcus α-haemolyticus bacteria are the most common bacteria found after an impacted mandibular third molar surgery. Red betel (Piper Crocatum) leaves extract is one of natural ingredients that contain several active components, such as alkaloids, flavnoids, tannins and saponins, which could potentially become an alternative to anti-microbes medicine. Aim: The aims of this research are to determine the number of Streptococcus α-haemolyticus bacteria found after an impacted mandibular third molar surgery and to conduct a study on red betel (Piper Crocatum) leaves extract and its potential to become an herbal anti-bacteria medicine against Streptococcus α-haemolyticus. Method: Swabs of Streptococcus α-haemolyticus bacteria were spread out on different plates of blood agar test. Several ± 1mm holes were created in the plated agar blood. These holes then filled with extract of red betel (Piper Crocatum) leaves differing in concentrations. Different concentrations used for red betel (Piper Crocatum) leaves extract were 6.25%, 12.5% and 25%. Distilled water was also added into the holes with the extract. The plates then incubated in a 37oC environment for 24 hours. Results: Streptococcus α-haemolyticus bacteria was found in 37 out of 40 patients, or at 92.5% rate, that were subjected to mandibular third molar surgery. The analysis using one-way ANOVA shows significant impacts on the growth of Streptococcus α-haemolyticus bacteria after an application of red betel (Piper Crocatum) leaves extract post mandibular third molar surgery (p<0.05).