Objective: Medication-related osteonecrosis of the jaw (MRONJ) is the condition of bone exposure which lasts more than 8 weeks which can be associated with clinical symptoms like pain, erythema, and infection. In addition to physiologic changes of hard and soft tissue cells, some different etiologic factors have been suggested for MRONJ; although, with no certain etiologic factor yet. Our aim is to determine the microbial etiologic roles in MRONJ through a systematic review of the etiologic roles of bacterial microorganisms in MRONJ conditions. Data Sources: An electronic search was done on January 15, 2018, at the databases of Cochrane Library, Google Scholar, PubMed (NCBI) and Scopus. Study Selection: Only in-vitro studies, clinical trials, and prospective and retrospective case reports were included in this review. Data Extraction: A meta-analysis could not be accomplished due to the lack of quantitative evidence and broad heterogeneity of study types, bacterial strains, treatment options and outcomes of these studies. Data Synthesis: A qualitative report of studies’ information has been established in 2 tables. Conclusion: The most frequent bacterial species indexed in our literature were Actinomyces genus, Parvimonas micra, and Streptococcus anginosus. Yet, there is no definite causal relationship between these microorganisms and osteonecrosis of the jaw (ONJ). Also, there are controversies about the treatment options, either to use the antibiotic therapy in association with antimicrobial agents (mouthrinses etc.) besides the standard surgical procedure or not. There needs to be more quantitative results reported in future studies in order to achieve more certain notions about the etiologic role of bacterial microorganisms in MRONJ patients.