Recently, antimicrobial photodynamic therapy (aPDT) as an alternative treatment modality has been used adjunctively in the treatment of periodontitis and peri-implantitis. Photosensitizing agents in the form of nanoparticles are designed for improving the efficiency of aPTD. Graphene quantum dots are a special type of tiny nanocrystals that can promote aPDT when coupled with curcumin (Cur). The main objective of the present study was to investigate the effects of photoexcited GQD-Cur on the metabolic activity of perio-pathogen mixed biofilms.GQD-Cur was synthesized and characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectrometry (UV-Vis), and X-ray diffraction (XRD). The cell cytotoxicity effect of GQD-Cur was evaluated on primary human gingival fibroblast (HuGu) cells. Perio-pathogen mixed biofilms including Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia photosensitized with GQD doped with Cur were irradiated with a blue LED at a wavelength of 435 ± 20 nm for 1 min, and then bacterial viability measurements were performed. The antimicrobial susceptibility profile, biofilm formation ability, amount of reactive oxygen species (ROS) released, and variations of gene expressions involved in biofilm formation were assessed.The SEM, DLS, FTIR, UV-Vis spectrometry, and XRD pattern confirmed that GQD-Cur was synthesized successfully. According to the results, GQD-Cur exhibited no cytotoxicity against HuGu cells. Photoexcited GQD-Cur resulted in a significant reduction in cell viability (93%) and biofilm formation capacity (76%) of peri-pathogens compared to the control group (P < 0.05). According to the results, a significant concentration-dependent increase in the ROS generation was observed in perio-pathogens mixed cells treated with different doses of GQD-Cur-aPDT. Moreover, rcpA, fimA, and inpA gene expression profiles were downregulated by 8.1-, 9.6-, and 11.8-folds, respectively.Based on the results, photoexcited GQD-Cur with a high potency of perio-pathogens suppression in planktonic and biofilm forms and downregulation of the biofilm genes expression pattern was exploited as a nanoscale-based platform for periodontitis.