Study objectives: Lemborexant (LEM) is a dual orexin receptor antagonist approved for treating adults with insomnia. We analyzed the efficacy (subjective sleep outcomes) and safety of LEM over 12 months in the subgroup of Asian subjects from Study E2006-G000-303 (Study 303). Methods: Study 303 was a 12-month, randomized, placebo-controlled (first 6 months), double-blind, parallel-group, phase 3 study of adults with insomnia disorder. During the 6-month Period 1, subjects were randomized (1:1:1) to placebo, LEM 5 mg (LEM5), or LEM 10 mg (LEM10); LEM subjects continued treatment in the following 6-month Period 2. Outcome measures included subject-reported (subjective) sleep onset latency (sSOL), sleep efficiency (sSE), wake after sleep onset (sWASO), total sleep time (sTST), Insomnia Severity Index (ISI), and Patient Global Impression–Insomnia version (PGI-I). Treatment-emergent adverse events (TEAEs) were assessed. Results: Overall, 178 Asian subjects (Japanese, n = 161; Chinese, n = 4; other Asian, n = 13) were included. Greater decreases in sSOL and sWASO and increases in sSE and sTST from baseline were observed with LEM vs placebo at 6 months; LEM benefits were sustained through 12 months. Greater decreases in ISI total score were seen with LEM vs placebo at 6 months; improvements from baseline with LEM continued through 12 months. For each PGI-I item, LEM-treated subjects had more positive medication effects than placebo-treated subjects at 6 months; these effects were maintained with LEM in Period 2. TEAEs were generally mild to moderate. Conclusions: LEM improved subjective sleep parameters and was well-tolerated in Asian subjects with insomnia disorder over 12 months. Clinical trial registration: ClinicalTrials.gov, NCT02952820; ClinicalTrialsRegister.eu, EudraCT Number 2015-001463-39.