Background In the Democratic Republic of the Congo (DRC), health care financing relies heavily on out-of-pocket payments, limiting access to essential services. In a context of declining external funding and ongoing efforts toward Universal Health Coverage (UHC), understanding households willingness to pay (WTP) for health care is critical for designing sustainable financing strategies. This study aimed to assess WTP for primary health care services and identify its associated factors in Eastern Kasai Province. Methods A cross-sectional study based on the contingent valuation method was conducted from 10 to 30 July 2025 among 633 randomly selected households using a multistage probabilistic sampling approach. Data were collected through semi-structured interviews using KoboToolBox. WTP was assessed using a stated preference approach. Logistic regression analyses using R 4.5.0 were performed to identify factors associated with WTP at a significance level of p < 0.05. Adjusted odds ratios (aORs) with 95% confidence intervals (95% CI) were reported. Results Overall, 70% of household heads reported willingness to pay for their own health care, and 73% for other household members. WTP decreased significantly as the cost of services increased, dropping from 95.5% for free care to 6.3% at the highest cost levels (above CDF 230,000). Poor perceived quality of care was a consistent reason for refusal, alongside financial constraints such as low income and indebtedness. Multivariable analysis showed that having a professional activity (OR = 1.9; 95% CI: 1.2-3.0; p = 0.006), residence in rural areas (OR = 2.1; 95% CI: 1.3-3.7; p = 0.008), and higher household income (OR = 2.2; 95% CI: 1.2-4.0; p = 0.011) were significantly associated with WTP. Despite relatively low absolute health care costs, the majority of households perceived them as high. Conclusion Willingness to pay for health care services in Eastern Kasai is moderate but highly sensitive to cost and strongly influenced by socioeconomic conditions and perceived quality of care. These findings underscore the need to strengthen financial protection mechanisms, particularly prepayment and risk-pooling systems, while improving service quality to enhance health care utilization and progress toward UHC in the DRC.