Serological proteome analysis (SERPA) is a classical immunoproteomics approach used to evaluate the humoral immune response to disease, vaccination, or administration of therapeutics. The method is disease agnostic, with the most common applications being the study of infectious diseases, cancers, and autoimmune disorders. The combination of two-dimensional western blotting and mass spectrometry analysis allows for the identification of individual antigens responsible for generating antibody responses. The identified immunoreactive proteins can be leveraged for the production of subunit vaccines, for use as correlates of vaccine protection, and as biomarkers for disease diagnosis. This chapter provides step-by-step instructions for performing SERPA, with additional notes providing insights gained from over two decades of experience using and optimizing the method.