Jaminan Kesehatan Nasional (JKN) is a national health insurance scheme that was launched in 2014 by the Government of Indonesia (GOI). The aim of the scheme is to provide insurance to the entire Indonesian population and to protect it from health-related financial shocks. A new insurance carrier, BPJS Kesehatan, has been established to implement the scheme. In 2014 the JKN scheme exhibited a rather large financial deficit with a medical claim ratio of 115%. This policy brief presents an assessment of the medium-term financial sustainability of JKN over the next five years. In our actuarial analysis and projection of health service claim data we assume that there will be an increase in the number of JKN members, increased utilisation of health care services and moderately higher health care unit costs. Based on these assumptions, we project that the deficit incurred in 2014 will continue to grow in the next few years and that this trend may jeopardise the health insurance scheme. To ensure the financial sustainability of JKN, a careful scrutiny of multiple factors, such as health care unit prices, and the implementation of reasonable cost-containment measures are necessary. This brief aims to examine the evidence of the scheme’s mid-term financial sustainability and to suggest further practical health policy options.