Vitamin D regulates calcium and immune function. While vitamin D deficiency has been associated with periodontitis, little information exists regarding its effect on wound healing and periodontal surgery outcomes. This longitudinal clinical trial assessed outcomes of periodontal surgery and teriparatide administration in vitamin-D-sufficient and -insufficient individuals. Forty individuals with severe chronic periodontitis received periodontal surgery, daily calcium and vitamin D supplements, and self-administered teriparatide or placebo for 6 wks to correspond with osseous healing time. Serum 25(OH)D was evaluated at baseline, 6 wks, and 6 mos post-surgery. Clinical and radiographic outcomes were evaluated over 1 yr. Placebo patients with baseline vitamin D deficiency [serum 25(OH)D, 16-19 ng/mL] had significantly less clinical attachment loss (CAL) gain (-0.43 mm vs. 0.92 mm, p < 0.01) and probing depth (PPD) reduction (0.43 mm vs. 1.83 mm, p < 0.01) than vitamin-D-sufficient individuals. Vitamin D levels had no significant impact on CAL and PPD improvements in teriparatide patients at 1 yr, but infrabony defect resolution was greater in teriparatide-treated vitamin-D-sufficient vs. -deficient individuals (2.05 mm vs. 0.87 mm, p = 0.03). Vitamin D deficiency at the time of periodontal surgery negatively affects treatment outcomes for up to 1 yr. Analysis of these data suggests that vitamin D status may be critical for post-surgical healing. (ClinicalTrials.gov number, CT00277706)