<p>Cancer stem cells (CSCs) pose a formidable therapeutic challenge as a treatment-resistant subpopulation that is critical for tumor recurrence and metastasis. A theranostic approach, unifying diagnosis and treatment in a single strategy, presents a viable pathway to overcome this obstacle. This review focuses on engineered extracellular vesicles (EVs), particularly exosomes, as an emerging and flexible platform for CSC theranostics. We examine recent advances in EV engineering that enhance their utility as both sensitive biomarkers for CSC detection and targeted delivery vehicles for anticancer agents. Furthermore, we discuss the development of synthetic EVs designed to counteract the pro‑tumorigenic functions of natural CSC‑derived EVs, which drive angiogenesis, metastasis, and therapy resistance. Finally, we evaluate the translational pathway for EV‑based theranostics, highlighting their significant clinical potential while also highlighting persisting challenges. Engineered EV platforms, by enabling simultaneous diagnosis and treatment, hold considerable promise as they leverage their dual roles as native biomarkers and customizable drug delivery systems.</p> Graphical Abstract <p></p>