Cancer stem cells (CSCs) represent the main target of the current efforts to eradicate cancer, because of their ability to promote metastatic dissemination and survive cytotoxic therapies. Here, we highlight the potential of patient-derived CSCs as an in vitro and in vivo pre-clinical model and of liquid biopsy as a diagnostic, prognostic and predictive tool. We discuss recently developed therapeutic strategies aiming at specifically targeting the cancer stem cell population, particularly focusing on the latest advances in cancer immunotherapy. In fact, it is now widely accepted that the microenvironment plays an active role in supporting tumor progression. Hence, the crosstalk between CSCs and the host immune system is nowadays object of intensive study, with the aim to develop effective therapeutic strategies targeting the ability of CSCs to escape immune-surveillance through immunoediting.