PURPOSE: As high rates of vitamin D deficiency have been demonstrated in orthopedic patient cohorts, this study aimed to characterize the association between a diagnosis of hypovitaminosis D and primary rotator cuff tear (RCT), primary rotator cuff repair (RCR), and postoperative complications in different sex and age cohorts. METHODS: In this retrospective cohort study using PearlDiver, a nationwide administrative claims database, records for all patients aged 30 to 89 yr who received a diagnosis of hypovitaminosis D between January 1, 2011, and October 31, 2018, were queried. Rates of primary RCT, primary RCR, and postoperative complications including subsequent surgery were calculated within sex- and age-specific cohorts and compared with matched control cohorts using multivariable logistic regression. RESULTS: Among the 336,320 patients included in the hypovitaminosis D cohort, these patients were significantly more likely to experience an RCT (odds ratio (OR), 2.70; 95% confidence interval (CI), 2.55-2.85) as well as a full-thickness RCT (OR, 2.36; 95% CI, 2.17-2.56) specifically within 2 yr of their diagnosis. Women with hypovitaminosis D were more likely to undergo surgery to address their full-thickness tears (OR, 1.37; 95% CI, 1.09-1.74). There was no difference in the rates of revision RCR or irrigation and debridement. However, women with hypovitaminosis D were significantly more likely to undergo manipulation under anesthesia (OR, 1.16; 95% CI, 1.03-1.31). CONCLUSIONS: Patients diagnosed with hypovitaminosis D were significantly more likely to suffer from a primary RCT and to undergo manipulation under anesthesia within a year of their RCR. Although many risk factors for RCT are unmodifiable, vitamin D deficiency is a readily modifiable risk factor with several treatment regimens demonstrating positive effects on musculoskeletal health.