Background: The prevalence of vitamin D deficiency in nursing home residents ranges from 79% to 98%. Objectives: The aim of this cross-sectional observational study in somatic and psychogeriatric nursing home residents was to determine the efficacy of a standardized oral vitamin D dosing regimen (VDDR) consisting of a loading dose (LD) of cholecalciferol 200,000 IU followed by a maintenance dose (MD) of 100,000 IU every 13 weeks in obtaining and maintaining an adequate and safe vitamin D trough level (VDTL), defined as 75–220 nmol/L (reference range). Methods: Blood samples of nursing home residents who had received the LD followed by at least one MD were analyzed for VDTL, calcium, parathyroid hormone, and creatinine. Data on age, sex, race, body weight and height, co-morbidity, co-medication, number of MDs, calcium supplementation, smoking, and use of alcohol were obtained from patient charts. The primary outcome for the efficacy of the VDDR was the percentage of nursing home residents with a VDTL 75–220 nmol/L, with a target percentage of 85% for the dosing regimen to be considered efficacious. Results: In 91 (58%; 95% confidence interval [CI] 50–66) of 156 included nursing home residents, a VDTL within the reference range was measured (mean [standard deviation] 81  nmol/L, range 13–150 nmol/L). The only variable that was identified as a significant risk indicator for obtaining a VDTL ≥ 75 nmol/L was the number of MDs being four or more (≥ 4 vs. < 4; odds ratio 2.7; 95% CI 1.4–5.3). Conclusion: This standardized VDDR was not efficacious in obtaining and maintaining an adequate VDTL in this nursing home resident population. Clinical trials registration number: NTR6029 (The Netherlands National Trial Register).