Background We evaluated the safety and efficacy of the anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor (TKI) brigatinib in Japanese patients with TKI-naive ALK -positive non-small cell lung cancer (NSCLC) from the phase 2, open-label, single-arm, multicenter J-ALTA study. Methods In the TKI-naive cohort of J-ALTA, the primary end point was independent review committee (IRC)-assessed 12-month progression-free survival (PFS). Secondary end points included objective response rate (ORR), intracranial response, overall survival (OS), and safety. Results The data were cut approximately 12 months after last patient enrollment. Thirty-two patients with ALK TKI-naive ALK -positive NSCLC were enrolled (median age range, 60.5 29–85 years; median duration of follow-up, 14.2 3.2–19.3 months; median treatment duration, 13.8 0.4–19.3 months). IRC-assessed 12-month PFS was 93.0% (90% confidence interval (CI) 79.2–97.8%); ORR, 96.9% (95% CI 83.8–99.9%), 12-month OS, 96.9% (95% CI 79.8–99.6%), and median OS was not reached. Of five patients with measurable baseline CNS metastases, two had partial intracranial response. The most common treatment-emergent adverse events were increased blood creatine phosphokinase (81%), hypertension (59%), and diarrhea (47%). Grade ≥ 3 adverse events occurred in 91% of patients; pneumonitis was reported in 3 (9%) patients. Conclusions In the J-ALTA TKI-naive cohort, brigatinib demonstrated clinically meaningful efficacy consistent with the international phase 3 study. The safety profile in Japanese patients was consistent with previous studies. Brigatinib is an important first-line option for Japanese patients with ALK -positive NSCLC. Clinical registration NCT03410108