The immunomodulatory, antiproliferative, and antiviral properties of interferons alpha (IFN-α) have made these cytokines attractive for numerous clinical applications. However, most of the current available IFN pharmaceutical dosage forms need to be injected frequently and may provoke adverse reactions in patients. This problem might be overcome by using biodegradable microspheres loaded with IFN. The encapsulation of IFN-α in microspheres and the current status of this technology are the main subjects reviewed here. To this end, we describe (i) the main methods and experimental parameters used to obtain IFN-loaded microspheres and (ii) characterization of these microspheres in terms of morphology, particle size, loading/encapsulation efficiency, residual water content, residual solvent content, release profile, and sterility. Also, we discuss both the characterization of the encapsulated IFN and the stabilization/protection of IFN during microencapsulation. Finally, a brief overview of preclinical and clinical studies using IFN-containing microspheres is given.