Oral biofilms formed by Streptococcus gordonii on removable dentures pose significant challenges, particularly for elderly individuals. Natural plant extracts, such as those from Salvadora persica and Juglans regia, have been explored for their potential antibacterial and antibiofilm activities. The biofilm-forming ability of S. gordonii isolated from elderly dentures was qualitatively and quantitatively assessed. The antibacterial and antibiofilm activities of S. persica and J. regia extracts were evaluated using a broth microdilution assay. Additionally, the effect of the extracts on artificial biofilms adhered to resin composite surfaces was examined and visualized using an environmental scanning electron microscope. Data revealed that S. gordonii biofilms adhered to artificial surfaces were less sensitive to the plant extracts compared to their planktonic counterparts. However, both planktonic and biofilm forms of S. gordonii exhibited increased susceptibility in the presence of J. regia extract, which demonstrated higher activity than S. persica. These findings highlight the potential of J. regia and S. persica extracts as natural antiplaque agents, particularly in oral care products designed for elderly denture wearers. Further research is warranted to explore their applications in daily oral hygiene.