Environmental performance indicators (EPIs) can be an important tool for evaluating and reporting the integration of environmental practices and tools in the defence sector, ensuring that environmental issues are being consistently and clearly followed into sector activities on a local and national scale. However, proper use of indicators is dependent on a suitable conceptual framework to manage and assess the environmental performance. Furthermore, monitoring is fundamental to environmental efficiency evaluations both to assess adherence to standards and to support management options. The use of EPI assures that a monitoring system for a public sector addresses only the key variables associated with significant environmental impacts and also improves communication with stakeholders. The main objective of this paper is to develop EPIs supported by an environmental information system (EIS), as a tool for environmental efficiency evaluations in the defence sector. To put the proposed approach into practice, the Norwegian defence EIS is used as a data source – a system developed to increase environmental awareness and to promote environmental efficiency, in the reporting of environmental aspects like use of ammunition, generation of waste, energy consumption, fuel consumption, use of chemicals, and water consumption. Use of real data acquired from the EIS is used to test and evaluate the robustness of the public sector's environmental performance indicator conceptual framework (SEPIIS), used to support the developed indicators. The main findings show how an indicator framework can be effectively combined with the use of an EIS designed to process data from a sector's activities, stressing how environmental issues could be integrated into overall public services performance management. The EPI developed for the Norwegian defence allowed to trace the sector's environmental performance, by comparisons with commissions from the Norwegian Ministry of Defence and national goals for GHG emissions, identifying areas for priority response measures. This joined approach of indicators and information systems could be useful to increase and improve environmental ex post and ex ante assessments, reporting and communication of defence activities.