For a study, it was determined that in the United States, little was known about seasonal variation in atrial fibrillation (AF) and whether the quality of AF management varies by season. The American Heart Association created the GWTGAFib (Get With The Guidelines–AFib) registry to improve national guideline adherence for the treatment and management of AF. From 2014 to 2018, researchers looked at 61,291 patients admitted to 141 participating hospitals across the United States. The outcomes were a number of AF admissions and quality-of-care metrics (defect-free treatment, defined as a patient obtaining all qualifying measures). For quality‐of‐care measures, generalized estimating equations accounting for within‐site correlations were used to estimate odds ratios (ORs) with 95% CIs, adjusting patient and hospital characteristics. Each season had a similar number of AF admissions, with the highest rate of AF admissions occurring in the fall (spring 25%, summer 25%, fall 27%, and winter 24% ). Overall, AF admissions were consistent across seasons, with little seasonal change. There was no seasonal fluctuation in the incidence of AF. There were no seasonal changes in care quality (multivariable-adjusted ORs and 95% CIs for winter, summer, and fall, respectively, were 0.93 (0.87–1.00), 1.09 (1.01–1.18), and 1.08 (0.97–1.20). There was no seasonal fluctuation in hospital admissions for AF or the quality of care for AF in a countrywide quality improvement registry.