Periodontitis seriously affects oral health and quality of life. MiRNAs have demonstrated a key role in regulating gene expression. To analyze and explore the expression characteristics of miR-511-5p in periodontitis and its potential mechanism of action. This study screened for miRNAs using the GSE89081 dataset. Clinical samples were collected to measure the expression levels of miR-511-5p. The diagnostic potential of miR-511-5p in periodontitis was evaluated through receiver operating characteristic (ROC) curve analysis. TargetScan was employed to predict the downstream target genes of miR-511-5p. The direct interaction between miR-511-5p and SOST was validated using a dual-luciferase reporter assay. Their correlation was assessed using Pearson correlation analysis. Cell viability was assessed by CCK-8 assay. IL-6, IL-1β, and TNF-α expression levels were quantified using RT-qPCR and ELISA assays. miR-511-5p was downregulated in the gingival crevicular fluid obtained from patients with periodontitis. The ROC curve analysis revealed that miR-511-5p could effectively discriminate between patients with periodontitis and healthy controls. SOST has been identified as a downstream target gene of miR-511-5p. The binding interaction between them was validated through a dual-luciferase reporter assay, and the Pearson correlation analysis revealed a negative correlation. The mimic of miR-511-5p enhanced the proliferation of PDLCs and suppressed the LPS-induced expression of IL-6, IL-1β, and TNF-α, whereas overexpression of SOST exerts opposing effects. miR-511-5p, as a potential biomarker for periodontitis, inhibited the proliferation and inflammatory response of PDLCs by negatively regulating SOST through targeting.