Precise characterization of proteins and proteoforms within the protein corona is essential for developing safer and more effective nanomedicines for diagnostic and therapeutic applications. Although the protein corona phenomenon has been recognized in nanomedicine for nearly two decades, the application of top-down proteomics to analyze proteoforms within this context has only recently gained traction. In this study, we advance proteoform-level analysis of the protein corona by integrating mass spectrometry (MS)-based top-down proteomics (TDP) and bottom-up proteomics (BUP). To demonstrate the performance of this approach, we generated large TDP and BUP datasets of protein corona of polystyrene nanoparticles (PSNPs) by analyzing breast cancer human plasma samples at various stages.