Aim: In 2017, Taiwan’s National Health Insurance Administration (NHIA) extended the Predetermined Treatment Duration Limit (PTDL) for bevacizumab in metastatic colorectal cancer (mCRC) from 24 to 36 weeks. However, its impact on treatment continuity and survival outcomes remains unclear. In this population-based cohort study, we evaluated the effects of PTDL relaxation on survival outcomes, first-line treatment continuity, and bevacizumab therapy duration in patients with mCRC. Methods: Using the Taiwan Health and Welfare Database, we identified two cohorts based on initial bevacizumab prescription dates: PTDL-24 weeks (April 1, 2013–March 31, 2016; N = 2,051) and PTDL-36 weeks (April 1, 2017–March 31, 2020; N = 2,484). We assessed overall survival (OS), progression-free survival (PFS), and time on treatment (ToT) for first-line therapy over 2 years. A doubly robust approach was applied, including inverse probability of treatment weighting (IPTW) to balance covariates, and Cox proportional hazards models adjusted for time trends. A two-stage residual inclusion (2-SRI) model estimated the impact of the policy on bevacizumab duration and subsequent survival outcomes. Results: After IPTW adjustment, baseline characteristics were well-balanced. The 36-week PTDL policy was associated with improved PFS (adjusted hazard ratio: 0.814 [95% confidence interval: 0.691–0.959]) and ToT (0.821 [0.703–0.959]), but not OS (0.926 [0.751–1.142]). The 2-SRI analysis showed the policy extended bevacizumab treatment by approximately 8 weeks, improving OS (0.912 [0.89–0.934]), PFS (0.941 [0.923–0.959]), and ToT (0.966 [0.95–0.984]). Conclusion: Relaxing the PTDL improved PFS and ToT by extending bevacizumab treatment exposure.