Conjugated polymers are attracting worldwide attention due to their potential for use as the active layer in advanced electronic, optoelectronic, and energy harvesting applications, and their cost-effective and low thermal budget processing traits. As the technologies based on these materials develop, new and more sensitive characterization techniques are needed. Recent progress on the use of spectroscopic ellipsometry as a highly sensitive and non-invasive method to obtain fundamental information about conjugated polymer films is reviewed. After a brief introduction to the practical details of the technique, the use of ellipsometry to determine optical parameters that provide insight into film morphology is described, including physical phase and molecular orientation, and resulting electronic structure. The characterization of layered systems and the use of in-situ ellipsometry as a means to gain understanding of the kinetics that occur during film deposition and post-deposition thermal and solvent vapor treatment is also discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.