Magnetic nanoparticles represent one of the most advanced developments in the application of nanotechnology to human health. To date, their clinical application has been restricted to the diagnosis of hepatic lesions and lymph node metastasis but functionalization of these materials with biomolecules as targeting motifs, and the inclusion of therapeutic drugs in their composition, is certain to make a substantial impact within biomedicine. One of the diseases that could benefit from these advances is cancer, as early diagnosis and effective treatment are crucial for a patient's survival and quality of life. This review will examine the recent uses of magnetic particles in cancer diagnosis and treatment.