BACKGROUND: The National Quality Forum endorsed a 3-item Care Transitions Measure (CTM-3), part of the Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) survey, for evaluating hospital care transitions performance. OBJECTIVE: To explore whether CTM-3 scores are a suitable proxy for quality of transitional care. DESIGN: Retrospective cohort study. PARTICIPANTS: A random sample of 48,384 adults discharged from medical or surgical wards in all 113 acute care hospitals in Alberta, Canada, between April 2011 and March 2016. MAIN MEASURES: CTM-3 scores and their associations with all-cause emergency department (ED) visits or nonelective readmissions at 30 days, 3 months, and 12 months anywhere in the province. RESULTS: CTM-3 scores were significantly lower (all p < 0.01) for females, older patients, those discharged from medical wards or teaching hospitals, and those with longer length of stay, higher Charlson scores, prior ED visits/hospitalizations, or who did not return to independent living after discharge. CTM-3 scores were not significantly associated with outcomes at 30 days (mean score 77.5 in those who subsequently had an ED visit/readmission vs. 77.9 in those who did not, p = 0.13, aOR 0.99, 95% CI 0.99-0.99). Although CTM-3 scores were significantly lower in patients who subsequently had ED visit/readmission at 3 months (77.5 vs. 78.5) and 12 months (77.6 vs. 79.5), the magnitude of risk was small: for every 10 point decrease in the CTM-3 score, the risk of ED visit/readmission was 2.6% higher (aOR 1.03, 95% CI 1.01-1.05) at 3 months and 4.0% higher (aOR 1.04, 95% CI 1.01-1.08) at 12 months. CONCLUSIONS: The CTM-3 score is influenced by baseline patient and hospital factors, is not associated with 30-day post-discharge outcomes, and is only weakly associated with 3-and 12-month outcomes. These findings suggest that the CTM-3 score is not a good performance measure for the quality of transitional care.