Cubosome particles were produced by fragmenting a cubic crystalline phase of glycerol monooleate and water in the presence of a stabilizing poly(ethylene oxide)-based polymer. The aim of our investigation was to study the interaction between these particles and mucin to gain information on how they would perform as a vehicle for mucosal drug delivery. Particle electrophoresis was used to investigate the interactions between particles and mucin in solution, and ellipsometry was utilized to study the interactions between particles and mucin-coated silica surfaces. The interaction studies were performed at relevant physiological conditions, and the pH and ionic strength were varied to gain more information about the driving forces for the interaction. The results from electrophoretic measurements showed that mucin in solution adsorbed to the particles at pH 4, whereas at pH 6 no clear interaction was detected. From ellipsometric measurements it was evident that the particles adsorb reversibly to a mucin-coated silica surface at pH 4, while no adsorption of particles could be detected at pH 6. The overall conclusion is that the interaction between these particles and mucin is weak and pH-dependent. These findings are in agreement with other investigations of the interactions between mucin and poly(ethylene oxide) chains.