BACKGROUND: Indonesia implemented one of the world's largest single-payer national health insurance schemes (the Jaminan Kesehatan Nasional or JKN) in 2014. This study aims to assess the incidence of catastrophic health spending (CHS) and its determinants and trends between 2018 and 2019 by which time JKN enrolment coverage exceeded 80%. METHODS: This study analysed data collected from a two-round cross-sectional household survey conducted in ten provinces of Indonesia in February-April 2018 and August-October 2019. The incidence of CHS was defined as the proportion of households with out-of-pocket (OOP) health spending exceeding 10% of household consumption expenditure. Chi-squared tests were used to compare the incidences of CHS across subgroups for each household characteristic. Logistic regression models were used to investigate factors associated with incurring CHS and the trend over time. Sensitivity analyses assessing the incidence of CHS based on a higher threshold of 25% of total household expenditure were conducted. RESULTS: The overall incidence of CHS at the 10% threshold fell from 7.9% to 2018 to 4.4% in 2019. The logistic regression models showed that households with JKN membership experienced significantly lower incidence of CHS compared to households without insurance coverage in both years. The poorest households were more likely to incur CHS compared to households in other wealth quintiles. Other predictors of incurring CHS included living in rural areas and visiting private health facilities. CONCLUSIONS: This study demonstrated that the overall incidence of CHS decreased in Indonesia between 2018 and 2019. OOP payments for health care and the risk of CHS still loom high among JKN members and among the lowest income households. More needs to be done to further contain OOP payments and further research is needed to investigate whether CHS pushes households below the poverty line.