OBJECTIVES: To compare the cost-effectiveness of population screening for vitamin D insufficiency with that of universal vitamin D supplementation in community-dwelling older adults. DESIGN: A Markov decision model simulating follow-up over a 36-month period. Published data were used to estimate values for the model, including costs (measured in 2011 U.S. dollars), utilities (measured in quality-adjusted life years (QALYs)), and probabilities. SETTING: Decision analysis simulation from a societal perspective. PARTICIPANTS: Hypothetical cohort of community-dwelling women and men aged 65 to 80. MEASUREMENTS: Net monetary benefit (NMB) was calculated by subtracting the incremental cost of the strategy from the product of incremental QALYs and willingness-to-pay threshold. A higher NMB indicates greater cost-effectiveness. RESULTS: In women aged 65 to 80, population screening was slightly more cost-effective than universal supplementation, with an incremental NMB of $224 compared with $189 (P < .001). Population screening in men was also more cost-effective than universal supplementation (incremental NMB $298 vs $260, P < .001). Results differed according to age group. In those aged 65, population screening had cost-effectiveness similar to that of universal supplementation in women ($59 vs $71) and men ($114 vs $120), whereas in those aged 80, population screening was substantially more cost-effective than universal supplementation in women ($563 vs $428) and men ($703 vs $571). CONCLUSION: Population screening and universal supplementation for vitamin D insufficiency are cost-effective strategies in community-dwelling older women and men. In the oldest old, population screening may be more cost-effective than universal supplementation.