Background Treatment patterns and outcomes of Graves’ disease (GD) are variable around the world. However, studies on treatment outcomes of GD from the Asian populations are limited. We aimed to evaluate treatment outcomes of GD in Thailand. Methods Patients with new diagnoses of GD in a single center between 2014–2018 were retrospectively reviewed. The diagnosis of GD was based on clinical features, which included diffuse goiter, Graves’ orbitopathy (GO), pretibial myxedema and acropachy. Results The age-adjusted incidence of GD was 26.57 per 100,000 per year. The study included 355 patients aged 15 years or above with a follow-up period of at least 24 months. Antithyroid drug (ATD) was the most popular first-line treatment modality with 98.7% patients receiving the treatment, followed by radioactive iodine (RAI) treatment in 1.3% patients. The most effective treatment modality was surgery with a remission rate of 100%. ATD had a lowest remission rate of 23.8%. Multivariable Cox regression analysis showed GO (HR 1.76, 95% CI 1.08–2.88) and initial TSH < 0.01 uIU/ml (HR 1.61, 95% CI 1.14–2.28) were significant factors associated with an increased treatment failure rate. Conclusion Treatment failure with ATD in patients with GD was frequent in this population. The diagnosis of GD based solely on clinical features may explain the high treatment failure rate in this study. More definitive treatment could be used to prevent relapse and complications of the disease.