Universal health coverage has become central to health policy debates, particularly as a strategy to protect households from financial hardship and impoverishment related to out-of-pocket (OOP) spending. Many low- and middle-income countries (LMICs), including India, have relied predominantly on publicly funded health insurance (PFHI) to improve financial protection against OOP spending. PFHI generally covers low-frequency, high-cost hospitalization expenses, even though non-hospitalization expenses are the main contributors to OOP. Global evidence suggests that stronger primary health care (PHC) provision is crucial for reducing catastrophic health expenditure (CHE). This issue becomes particularly important in the context of climate-sensitive diseases (CSDs), whose incidence is increasing due to more frequent and extreme weather events, which may increase the risk of CHE. Objective: This study estimates the causal impact of publicly provided PHC and PFHI on CHE arising from CSDs. Methods: Using district-level data for all 640 Census districts in India, we applied propensity score matching and inverse probability weighting to compare the effects of PHC and PFHI on CHE associated with CSDs. Results: The findings show that strengthened PHC substantially reduces OOP spending and CHE associated with CSDs, whereas PFHI shows no statistically significant effect. Conclusion: These results highlight the need to prioritize climate-resilient PHC systems to address the escalating health impacts of climate change and advance equitable progress toward universal health coverage in LMICs.