Intratumoral microbiota plays a critical role in cancer initiation, progression, and treatment. This review explores the interactions between intratumoral microbiota and cancer, highlighting their contributions to tumor development and therapeutic outcomes. The intratumoral microbiome, which includes bacteria, fungi, and other microbes, influences cancer cell properties and immune system function within the tumor microenvironment (TME). Research indicates that intratumoral microbiota can originate from various sources, including mucosal barriers, the circulatory system, and adjacent normal tissues. The diversity of intratumoral microbiota varies among cancer types, with distinct microbial signatures associated with specific cancers. These signatures have potential diagnostic and therapeutic applications. Intratumoral microbiota can modulate cancer progression through various mechanisms, including DNA damage, activation of oncogenic pathways, and initiation of inflammation. These processes can either promote or suppress tumor growth, depending on the specific microbial composition. The microbiota also influences immune responses, affecting the effectiveness of immunotherapy. For example, certain bacteria can enhance or inhibit immune cell activity, impacting the overall immune response against cancer. The potential of intratumoral microbiota for tumor therapy is increasingly recognized. Strategies such as probiotics, antibiotics, and fecal microbiota transplantation are being explored to modulate the intratumoral microbiota and improve treatment outcomes. Engineered bacteria are also being developed to deliver therapeutic agents directly to tumors, enhancing treatment specificity and efficacy. These approaches highlight the importance of understanding the complex interactions between intratumoral microbiota and cancer, offering new avenues for cancer treatment and management. Further research is needed to fully elucidate the mechanisms underlying these interactions and to develop more effective therapeutic strategies.Intratumoral microbiota plays a critical role in cancer initiation, progression, and treatment. This review explores the interactions between intratumoral microbiota and cancer, highlighting their contributions to tumor development and therapeutic outcomes. The intratumoral microbiome, which includes bacteria, fungi, and other microbes, influences cancer cell properties and immune system function within the tumor microenvironment (TME). Research indicates that intratumoral microbiota can originate from various sources, including mucosal barriers, the circulatory system, and adjacent normal tissues. The diversity of intratumoral microbiota varies among cancer types, with distinct microbial signatures associated with specific cancers. These signatures have potential diagnostic and therapeutic applications. Intratumoral microbiota can modulate cancer progression through various mechanisms, including DNA damage, activation of oncogenic pathways, and initiation of inflammation. These processes can either promote or suppress tumor growth, depending on the specific microbial composition. The microbiota also influences immune responses, affecting the effectiveness of immunotherapy. For example, certain bacteria can enhance or inhibit immune cell activity, impacting the overall immune response against cancer. The potential of intratumoral microbiota for tumor therapy is increasingly recognized. Strategies such as probiotics, antibiotics, and fecal microbiota transplantation are being explored to modulate the intratumoral microbiota and improve treatment outcomes. Engineered bacteria are also being developed to deliver therapeutic agents directly to tumors, enhancing treatment specificity and efficacy. These approaches highlight the importance of understanding the complex interactions between intratumoral microbiota and cancer, offering new avenues for cancer treatment and management. Further research is needed to fully elucidate the mechanisms underlying these interactions and to develop more effective therapeutic strategies.