The scientific validity of the Merit-Based Incentive Payment System (MIPS) quality score as a measure of hospital-level patient outcomes is unknown. To examine whether better physician performance on the MIPS quality score is associated with better hospital outcomes. This cross-sectional study of 38 830 physicians used data from the Centers for Medicare & Medicaid Services (CMS) Physician Compare (2017) merged with CMS Hospital Compare data. Data analysis was conducted from September to November 2020. Linear regression was used to examine the association between physician MIPS quality scores aggregated at the hospital level and hospitalwide measures of (1) postoperative complications, (2) failure to rescue, (3) individual postoperative complications, and (4) readmissions. The study cohort of 38 830 clinicians (5198 [14.6%] women; 12 103 [31.6%] with 11-20 years in practice) included 6580 (17.2%) general surgeons, 8978 (23.4%) orthopedic surgeons, 1617 (4.2%) vascular surgeons, 582 (1.5%) cardiac surgeons, 904 (2.4%) thoracic surgeons, 18 149 (47.4%) anesthesiologists, and 1520 (4.0%) intensivists at 3055 hospitals. The MIPS quality score was not associated with the hospital composite rate of postoperative complications. MIPS quality scores for vascular surgeons in the 11th to 25th percentile, compared with those in the 51st to 100th percentile, were associated with a 0.55-percentage point higher hospital rate of failure to rescue (95% CI, 0.06-1.04 percentage points; P = .03). MIPS quality scores for cardiac surgeons in the 1st to 10th percentile, compared with those in the 51st to 100th percentile, were associated with a 0.41-percentage point higher hospital coronary artery bypass graft (CABG) mortality rate (95% CI, 0.10-0.71 percentage points; P = .01). MIPS quality scores for cardiac surgeons in the 1st to 10th percentile and 11th to 25th percentile, compared with those in the 51st to 100th percentile, were associated with 0.65-percentage point (95% CI, 0.013-1.16 percentage points; P = .02) and 0.48-percentage point (95% CI, 0.07-0.90 percentage points; P = .02) higher hospital CABG readmission rates, respectively. In this study, better performance on the physician MIPS quality score was associated with better hospital surgical outcomes for some physician specialties during the first year of MIPS.