We evaluated the reported contraindications to early β-blocker use and associated mortality within and across patient age groups. Contraindications to early β-blocker use were evaluated in patients with non-ST-elevation acute coronary syndrome in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines (CRUSADE) initiative from February 2003 to December 2006. The prevalence, reasons, and trends in the contraindications were evaluated by age (≤65, 66 to 74, and ≥75 years). The associations between the reported contraindications and in-hospital mortality were determined within and compared across age groups using the logistic generalized estimating equations method, adjusting for baseline patient characteristics. Of 112,448 patients, 11,711 (10.4%) had a reported contraindication to early β-blocker use. The prevalence varied by age (≤65, 7.9%; 66 to 74, 10.6%; and ≥75, 13.4%; p <0.0001). No significant changes were seen over time, except for a small increase in patients ≤65 years (p = 0.001). Among the hospitals with >40 patients in the registry, the median hospital level rate of reported contraindications was 9.9% (interquartile range 6.7% to 14.3%). The distribution of rates was more widespread among the hospitals' older versus younger patients. In all age groups, a statistically significant greater association was found with in-hospital mortality in those with reported contraindications versus those without contraindications who received a β blocker (adjusted odds ratio 2.81, 95% confidence interval 2.28 to 3.46; adjusted odds ratio 2.50, 95% confidence interval 2.07 to 3.03; adjusted odds ratio 2.11, 95% confidence interval 1.88 to 2.37, for ages ≤65, 66 to 74, and ≥75 years, respectively). The strength of the association was similar across all age groups (interaction p = 0.19). The reported contraindications to early β-blocker use were common and increased with age. The contraindications were independently associated with greater in-hospital mortality, underscoring the importance of accurately identifying contraindications. In conclusion, the results did not indicate any disparity in reporting the contraindications according to patient age.