Local climate change mitigation plans can be essential in enabling sustainability transitions at the municipality level. However, existing frameworks for assessing the quality of climate plans inadequately address their potential to foster sustainability transitions. We develop an assessment framework consisting of indicators and associated questions by integrating elements of the transition management framework with essential quality dimensions of climate plans and planning processes identified through a literature review. We illustrate and validate the assessment framework by applying it to the climate plans of three medium-sized cities in Switzerland. Our findings demonstrate that the local climate change mitigation plans performed well regarding the tactical and operational indicators but were less optimal concerning strategic and reflexive indicators. Nevertheless, the transition management framework provided a useful framework contributing to a comprehensive and systemic assessment highlighting the importance of stakeholder involvement, inter-sectoral coordination, and monitoring and evaluation as a means for social learning.