Indonesia as the largest country and the highest population in the Southeast Asia region results in the greatest value of energy consumption, therefore, being a huge energy-consuming country may represent the situation in that region. Various kinds of energy policies have been carried out by the Government of Indonesia, resulting in a situation, where energy production, energy exports, energy access, are increased, while energy imports, energy reserves, and emission intensities are decreased. However, these situations have never been well concluded. The energy security index provides information that can summarize all of the energy situations. The aim of this paper is to conduct an assessment of Indonesia’s energy security index within the period of 2000–2018. The energy security index consists of dimensions, namely availability, affordability, accessibility, and acceptability. Each dimension consists of indicators, in which there are twelve indicators used in the assessment. All indicators and dimensions subject to the same weight, so that the selection of indicators is important to represent the energy situation in accordance with Indonesia’s perspective on energy security. The indicator normalization uses the min–max method, in which the maximum indicator obtained based on the highest value owned by countries in the Southeast Asia Region, therefore the indicator value will be relative to it. The results show an increase for almost all dimensions except the affordability dimension. In general, Indonesia’s energy security index has increased by 29.9%, which is 0.330 and 0.428 in the year of 2000 and 2018, respectively. The Indonesia’s energy security index showing a value below 0.5 indicates that Indonesia is in an unfavorable situation of energy security. Furthermore, the improvement of energy security should be focused on the dimension that has the lowest value.