Exosomes are extracellular vesicles that play a central role in mediating intercellular communication within the tumor microenvironment (TME). Cancer-derived exosomes carry proteins, nucleic acids, and lipids that reshape the phenotype and function of surrounding stromal and immune cells, thereby promoting tumor progression, angiogenesis, metastasis, and resistance to therapy. At the same time, exosomes derived from TME components, including macrophages, dendritic cells, B cells, T cells, fibroblasts, neutrophils, and NK cells, reciprocally influence tumor growth and immune evasion. These bidirectional interactions highlight exosomes as both drivers of tumor progression and regulators of antitumor immunity. In this review, we synthesize current evidence on the diverse mechanisms by which exosomes reprogram immune and stromal cells, with a focus on their dual roles in cancer biology. We also discuss emerging therapeutic strategies to inhibit exosome biogenesis, release, and function, underscoring their translational potential as novel targets for cancer diagnosis and treatment.