Aims: This study assessed hemoglobin A1c (HbA1c) across the lifespan in people with type 1 diabetes (T1D) in Germany/Austria, Sweden, and the United States between 2011 and 2017 to ascertain temporal and age-related trends. Methods: Data from the Diabetes-Patienten-Verlaufsdokumentation (DPV) (n = 25,651 in 2011, n = 29,442 in 2017); Swedish Pediatric Diabetes Quality Registry (SWEDIABKIDS)/National Diabetes Register (NDR), (n = 44,474 in 2011, n = 53,690 in 2017); and T1D Exchange (n = 16,198 in 2011, n = 17,087 in 2017) registries were analyzed by linear regression to compare mean HbA1c overall and by age group. Results: Controlling for age, sex, and T1D duration, HbA1c increased in the United States between 2011 and 2017, decreased in Sweden, and did not change in Germany/Austria. Controlling for sex and T1D duration, mean HbA1c decreased between 2011 and 2017 in all age cohorts in Sweden (P < 0.001). In the United States, HbA1c stayed the same for participants <6 years and 45 to <65 years and increased in all other age groups (P < 0.05). In Germany/Austria, HbA1c stayed the same for participants <6 to <13 years and 18 to <25 years; decreased for participants ages 13 to <18 years (P < 0.01); and increased for participants >= 25 years (P < 0.05). Conclusions: The comparison of international trends in HbA1c makes it possible to identify differences, explore underlying causes, and share quality improvement processes. National quality improvement initiatives are well accepted in Europe but have yet to be implemented systematically in the United States. However, disparities created by the lack of universal access to health care coverage, unequal access to diabetes technologies (e.g., continuous glucose monitoring) regardless of insurance status, and high out-of-pocket cost for the underinsured ultimately limit the potential of quality improvement initiatives.