Affinity enrichment techniques in combination with quantitative proteomics enable the unbiased identification of protein-protein interaction, and thus the delineation of protein complexes and interaction networks. Here, we describe an immunoaffinity enrichment approach that employs covalently immobilized antibodies for the identification of protein-protein interactions of endogenously expressed proteins under near-to-physiological conditions. Specifically enriched proteins are identified using shotgun mass spectrometry and isobaric mass tag-based relative quantification.