The present study aimed to evaluate proinflammatory cytokine and vitamin D levels in rheumatoid arthritis (RA) and chronic periodontitis (CP) patients and healthy individuals before and after initial periodontal treatment. Overall, 17 CP patients with RA (RA + CP), 18 systemically healthy CP patients (CP), and 18 healthy controls (C) were included. Clinical periodontal measurements were recorded and gingival crevicular fluid (GCF) and blood samples were recorded. RA + CP and CP patients received nonsurgical periodontal treatment. Vitamin D, tumor necrosis factor (TNF)-α, receptor activator of nuclear factor-KB ligand (RANKL), and OPG levels were determined in GCF and serum. Baseline clinical parameters were similar in all periodontitis groups (P > 0.05) but were higher than that in controls (P < 0.05). Periodontal treatment improved clinical parameters in all periodontitis groups (P < 0.05). GCF vitamin D levels were higher in RA + CP and CP groups than in healthy controls, but these levels decreased in the RA + CP group after periodontal treatment (P < 0.05). Serum RANKL and GCF TNF-α levels in RA patients decreased after periodontal treatment (P < 0.05). Within the limitations of this study, the results suggested that GCF vitamin D levels are increased in RA patients and decrease after periodontal treatment; therefore, local vitamin D levels might be an important indicator of periodontal bone loss.