Cities and local authorities are key players in addressing climate change. The Covenant of Mayors for Climate and Energy (CoM) has been the first initiative of its kind addressing local authorities to endorse their efforts in the implementation of sustainable energy and climate policies and to provide them with a harmonised data compilation, methodological and reporting framework, supporting them in translating mitigation and adaptation goals into reality.This report provides a scientific assessment of CoM regarding the pillars of mitigation and adaptation of climate change. The assessment describes the plans submitted by signatories, examines planned and implemented policies and gives an overview on the progresses in terms of energy consumption, GHG emission reduction and resilience increase. The key findings show that the overall commitment to reducing GHG emissions by signatories is 30% by 2020 and 47% by 2030, compared to baseline emissions projected to 2005. These commitments are more ambitious than the minimum requested targets. The adaptation pillar shows a recent reporting framework, therefore, further analysis in the future is needed once the number of signatories increases. The hazards reported the most in EU cities are extreme heat and droughts while the sectors at risk of impacts are reported to be water and health. Nevertheless, a clear gap exists between the hazards impacting specific sectors and sectors where actions are planned and implemented. A further development of the structure of the adaptation pillar and reporting system in place may support in bridging this gap.