The human body contains a range of organisms collectively known as the microbiome. These microorganisms, including bacteria, viruses, fungi, and protozoa, establish microbiota communities. One area where the microbiome is commonly found is the gastrointestinal tract. Gut microbiota interacts with the immune and nervous systems through complex pathways. These interactions involve signaling processes affecting cancer development and our bodies’ response to immunotherapy. The immune system regulates the microbiota population in response to their signalings. Although genetic mutations have been studied as an essential factor in the development of various cancers, recent studies have investigated the relationship between the microbiome and the immune system in cancer formation. The role of the microbiome in some cancers has been established. The change in the microbiome population, the presence of pathogenic species, and the production of different metabolites are factors that have been investigated. Various studies have been conducted to target the microbiome population and the metabolites produced by them to control cancer progression. Understanding the complex interactions between microorganisms and cancer cells promises new diagnostic and therapeutic strategies for various cancers.