Alectinib is a selective anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor as standard therapy for ALK-rearranged non-small cell lung cancer (NSCLC). Hemolytic anemia is considered as a rare but significant adverse event with alectinib. Here, we report a case of a 73-year-old female with lung adenocarcinoma, harbouring an ALK fusion gene, who received alectinib as second-line therapy and developed gradually progressive grade 4 (6.4 g/dL) drug-induced hemolytic anemia (DIHA) after complete response. We discontinued alectinib and performed a blood transfusion for the severe anemia. The anemia improved with no recurrence of lung adenocarcinoma over 10 months. Regular hematologic monitoring and the possibility of DIHA should be considered in case of progressive hemolytic anemia during alectinib treatment.