Microalgae present a novel and multifaceted approach to cancer therapy by modulating the tumor-associated microbiome (TAM) and the tumor microenvironment (TME). Through their ability to restore gut microbiota balance, reduce inflammation, and enhance immune responses, microalgae contribute to improved cancer treatment outcomes. As photosynthetic microorganisms, microalgae exhibit inherent anti-tumor, antioxidant, and immune-regulating properties, making them valuable in photodynamic therapy (PDT) and tumor imaging due to their capacity to generate reactive oxygen species (ROS). Additionally, microalgae serve as effective drug delivery vehicles, leveraging their biocompatibility and unique structural properties to target the TME more precisely. Microalgae-based microrobots further expand their therapeutic potential by autonomously navigating complex biological environments, offering a promising future for precision-targeted cancer treatments. We position microalgae as a multifunctional agent capable of modulating TAM, offering novel strategies to enhance TME and improve the efficacy of cancer therapies.