Objective: The purpose of this study was to determine the antibacterial effect of a newly developed haemostatic agent Ankaferd Blood Stopper® (ABS) and Ferric Sulphate (FS) on various oral microorganisms. Study design: Bacterial strains were freshly incubated in their specific broth media. For each of the strains, 3 wells per each agent, with a 5 mm diameter were made under aseptic conditions in the specific agar media. Then they were filled with a test agents or 0.2% chlorhexidine digluconate (CHX) (control group). After 24h and 48h incubation periods, inhibition zones were measured. Results: ABS showed antibacterial effect on all test microorganisms except Lactobacillus acidophilus and Lactobacillus salivarius. Ferric sulphate and CHX have antibacterial effect on all microorganisms. When the test agents compared, the inhibition zones of the ABS were found smaller than the ferric sulphate and CHX. Conclusions: Although ferric sulphate and ABS have antibacterial effect, ferric sulphate had better antibacterial activity than ABS on oral microorganisms under in vitro condition. FS and ABS not only exhibit the haemostatic activity but also antimicrobial activity.