Climate change mitigation can be achieved through different instruments: policy requirements, technological approaches to minimise greenhouse gases, forestry and agriculture management, educational and public information activities and others. Government, funding institutions, enterprises, educational institutions and nongovernmental organisations play the crucial role in developing and operating the awareness raising platform focused on climate change mitigation. Objective of the research is to evaluate the role of six non-governmental organisations (NGOs), providing different services - consultative, financial, educational, in raising capacities in climate change field in Latvia: Environmental Consultative Council, Environmental Science and Education Council, Climate Change Financing Instrument Consultative Council, Tri-Party Cooperation Sub-Council on Environmental Protection Issues, Climate Technology Cooperation Council. The evaluation is structured used the main evaluation criteria widely used for assessment of the success of activities and projects in the field of the environment. These criteria are: relevance, effectiveness, efficiency, impact and sustainability. Within the research a combined evaluation methodology based on a criteria-based evaluation and multicriteria decision making technique TOPSIS is developed for determination of the most effective activities of the nongovernmental organisations for climate change mitigation.