Background: Alectinib and crizotinib have been approved as first-line therapies for advanced non-small cell lung cancer (NSCLC) with anaplastic lymphoma kinase (ALK) gene fusion. However, the therapeutic efficacy and side effects are still largely unknown of patients who switched to next-generation ALK tyrosine kinase inhibitors (ALK-TKIs), such as alectinib, after experiencing no disease progression with initial crizotinib treatment. Methods: This prospective real-world study enrolled patients who were treated with alectinib after experiencing no disease progression with initial crizotinib treatment. The patients' baseline characteristics, objective response rate (ORR) of crizotinib and alectinib, size change of target tumor lesions, treatment regimen and adverse events (AEs) were collected and analyzed. Results: The study included 53 patients, the majority of whom (96.2%) had non-squamous NSCLC. The median age was 51 (range, 31-80) years old. The ORR of first-line crizotinib was 54.7%. The ORR of sequential alectinib was 73.6%, and 90.5% of patients showed further tumor shrinkage after the alectinib treatment. The median progression-free survival was not reached, and 90.5% of patients were still enrolled in the study at the last follow-up. Among them, 34.0% of patients switched to alectinib treatment due to the toxicity. Crizotinib was associated with a higher frequency of AEs of grades 3 and 4 than alectinib (15.1% vs. 0%). Neither group had any AEs resulting in death. Conclusions: Switching to alectinib might be an option for patients who do not experience disease progression with initial crizotinib therapy, and may promote better treatment compliance.