Background: Iraqi society suffers from a number of health issues, including dental caries, necrosis, and gingivitis. The treatment of bacteria has become difficult because of their resistance to many antibiotics. One of the most prevalent species in the mouth that causes dental caries is Streptococcus mutans. Objectives: The aim of this research was to isolate and diagnose Streptococcus mutans and study other Virulence factors such as catalase and blood hemolysis. Materials and Methods: Using biochemical tests and phenotypic diagnostics. Using biochemical tests and phenotypic diagnostics. The study included the collection oral swabs from (54) patients infected with teeth dental caries (A group) and dental prosthesis wearing patients (B group) at specialized dental hospital and dental clinics at was it province and both sexes. Results: The number of isolates was 14(25.92%) belonging to Streptococcus mutans, were identified by cultural methods, biochemical tests, Api 20 Strep. system and Vitek 2 compact system. The findings indicated that the all of the isolates had a not capacity for catalase production.