This study was conducted to identify the evidence and knowledge gaps in studies investigated mastitis, and quantify the prevalence of clinical mastitis (CM) and subclinical mastitis (SCM) in buffalo in Iraq. Databases used as search engines to track the studies included PubMed, CABI, IASJ, and Google Scholar. Additional pertinent studies identified via other methods were also considered for inclusion. Identified studies were divided into two main groups: (i) studies reported proportion of mastitis cases in lactating buffaloes, which were considered for meta-analysis; and (ii) studies that investigated presence of bacteria in milk sampled from buffaloes with different status of mastitis. A total of 17 studies were qualified for review; 9 reported proportion of mastitis episodes, and 13 isolated pathogenic bacteria in lactating buffalo milk. Prevalence of CM and SCM was 20.89% and 29.62%, respectively. The most isolated pathogens were Staphylococcus spp. (46.75%) followed by Streptococcus spp. and other miscellaneous bacteria at 32.96%, 19.04%, respectively. A substantial risk of bias was revealed in most of the identified studies. In conclusion, it is important to conduct further studies that apply standard epidemiological tools for estimating incidence and identifying risk factors of CM and SCM in buffaloes in Iraq.