Cancer is considered as one of the most widely distributed diseases among people regardless their cultural background. It causes high level of both morbidity and mortality and represents the second leading cause of worldwide death. Microbes are playing a significant role in cancer prompting, initiation, progression, and reaction to treatment. Reports correlating the microbiota and the causative links have emerged recently implying the variations of commensal microbes in tumorigeneses. Microbiota mainly affect the microenvironmental factors, regulating the epithelial to mesenchymal transition, altering some important physiological pathways (e.g., causing mutation in p53 (the tumor suppressive factor)), and also switching some functional genes from onco-suppressive to oncogenic effect. It is worthy to note that microbiota, microenvironmental factors, and the consequent chronic inflammation have been found to be closely related to cause a specific type of cancer (varied with varying the aforementioned factors). Hence, in the present chapter, some of the major types of cancer with their significantly causing microbial factors will be discussed.