This study systematically investigated the interactions of the tumor biomarker alpha-fetoprotein (AFP) and bovine serum albumin (BSA) with planar lipid membranes using neutron reflectometry, quartz crystal microbal- ance with dissipation monitoring, and atomistic molecular dynamics simulations. By examining a range of lipid compositions-including charged, neutral, and nanodomain-containing bilayers-we dissected the molecular mech- anisms governing protein-membrane interactions. AFP consistently exhibited stronger interactions than BSA. While both proteins showed negligible binding to zwitterionic POPC bilayers, BSA only interacted significantly with negatively charged POPS membranes. In contrast, AFP strongly engaged with both SM/CHOL nanodomains and POPS-containing bilayers, leading to protein incorporation and lipid extraction, respectively. On positively charged DOTAP membranes, AFP formed a stable adsorbed layer. These findings reveal how lipid composition modulates protein adsorption, insertion, and membrane integrity, offering new mechanistic insights into the dif- ferential binding affinities of AFP and BSA. The results underscore the importance of protein-lipid interactions in clinical assays for blood tumor biomarkers, as these interactions may influence the formation of protein-lipid complexes and impact detection accuracy. This work may guide the optimization of biosensing strategies, par- ticularly for glycosylated biomarkers, to enhance the sensitivity and reliability of clinical diagnostics.