Adsorption of antimicrobial peptide histatin 5 on a poly(methyl methacrylate) denture base may serve to prevent biofilm formation, leading to a reduction of denture-induced stomatitis. This study focused on adsorption behavior of histatin 5 onto PMMA surfaces modified using a cold plasma technique and the effectiveness of histatin 5 adsorption for reducing Candida albicans biofilm formation by the quartz crystal microbalance-dissipation (QCM-D) technique. PMMA spin-coated specimens were treated with oxygen (O(2)) plasma using a plasma surface modification apparatus. The amount of histatin 5 adsorbed onto the PMMA treated with O(2) plasma is more than six times greater than that adsorbed onto untreated PMMA. The degree of histatin 5 adsorption had a negative correlation with the contact angle, whereas that of zeta-potential showed no significant correlation. XPS analysis revealed that the introduction of the carboxyl and O(2) functional groups were observable on the O(2) plasma-treated PMMA. Increased surface hydrophilicity and the formation of the carboxyl could be responsible for histatin 5 adsorption on plasma-treated PMMA. There is no significant difference between histatin-adsorbed PMMA and control PMMA for C. albicans initially attached. On the contrary, the amount of C. albicans colonization on histatin-adsorbed PMMA was significantly less than the control.