The rising cost of healthcare in Malaysia has prompted significant policy reforms, including the introduction of co-payment mechanisms in health insurance by Bank Negara Malaysia effective September 2024. While co-payment is expected to reduce premiums and promote cost-sharing, its acceptance among insured patients remains uncertain. This study investigates the acceptance of insurance co-payment among patients visiting private General Practitioner (GP) clinics in Klang Valley using the Health Belief Model (HBM) as the theoretical framework. The research adopts a quantitative and qualitative, cross-sectional design, targeting adults aged 18–70 with active co-payment health insurance plans. A structured questionnaire was disseminated, encompassing socio-demographic data and HBM constructs such as perceived susceptibility, severity, benefits, barriers, and cues to action. Data analysis was performed using SPSS and Partial Least Squares Structural Equation Modelling (PLS-SEM) to examine relationships between variables and test proposed hypotheses. As for the qualitative analysis, coding and categorization of themes related to attitudes toward co-payment was performed and NVivo or manual coding was done for identifying recurring patterns. Preliminary literature suggests that socio-economic status, health literacy, and prior insurance experience strongly influence patient attitudes toward co-payment systems. Global comparisons show that co-payment adoption varies based on population awareness, affordability, and healthcare delivery models. This study fills a local research gap by evaluating the behavioural factors shaping co-payment acceptance within the Malaysian context. Findings are expected to inform healthcare policymakers and insurance providers on how to design more equitable and patient-sensitive health financing models. Insights from this study may enhance communication strategies, reduce perceived financial barriers, and support sustainable healthcare delivery. Keywords: Co-payment, Health Belief Model, Health Insurance, Patient Acceptance, Klang Valley