OBJECTIVES: To determine whether anticoagulation therapy improves outcomes in patients with coronavirus disease 2019 (COVID-19) in Japan given their lower risk of thrombosis compared with Western cohorts. METHODS: The efficacy of anticoagulation therapy in hospitalized patients with COVID-19 was evaluated using a nationwide registry: the COVID-19 Registry Japan. The inverse probability of weight treatment method was used to adjust for baseline confounders in the anticoagulation and non-anticoagulation groups. RESULTS: Of the 1748 patients included, anticoagulants were used in 367 patients (treatment group). The patients in the anticoagulant group were older, predominantly male, and often presented with obesity, hyperlipidaemia, hypertension, diabetes and elevated D-dimer levels. Twenty-nine-day mortality was 7.6% in the whole cohort (treatment group, 11.2%; no treatment group, 6.6%), 6% in patients who were not treated with steroids (treatment group, 12.3%; no treatment group, 5.2%), and 11.2% in patients treated with steroids (treatment group, 10.5%; no treatment group, 11.8%). Mortality in the whole cohort was similar between the treatment and no treatment groups (P=0.99), and an insignificant decreasing trend in mortality was observed in patients treated with steroids (P=0.075). CONCLUSIONS: Anticoagulants may be beneficial in Asians, in whom comorbidities and risk of thrombosis may differ from other ethnic groups.