Existing energy security index (ESI) studies focus on individual countries, with indicators chosen according to the specifics of the country or the region. This study assesses the ESI for district heating (DH) in Latvia through a composite index methodology. The index consists of 10 indicators, identified through a comprehensive literature review and subsequently adapted to the specific context of DH. Findings reveal distinct trends across dimensions. In the social dimension, household energy use per capita is predicted to increase to 8.5 MWh by 2050, while consumption per square metre will fall to 0.15 MWh/m2. The economic dimension shows steady improvement, with import dependency decreasing to 2.7 %, self-reliance rising to 62.1 %, and household heating costs falling from 38 % of income in 2010 to 3.9 % in 2050. The environmental dimension demonstrates the strongest progress: CO2 emissions per m2 decline from 14.76 t in 2010 to net zero by 2050, raising its sub-index from 0.16 to 1.0. The technical dimension improves in efficiency (1.4 MWh/MW by 2050) but faces declining energy source diversity, peaking in 2030 (0.78) and dropping to 0.43 by 2050. Overall, the DH ESI is lowest in 2020 (0.44) and highest in 2030 (0.64). Latvia's DH energy security (ES) is projected to strengthen in the long term, driven by economic and environmental gains from renewable energy expansion, efficiency improvements, and reduced import dependency. Vulnerabilities persist in the social and technical dimensions, underscoring the need for targeted policy measures to balance progress across all areas.