Learning from each other and knowledge exchange matter in achieving transitions toward more sustainability. Cycling promotion is substantive in these complex transitions. The thesis was a first attempt to examine and contribute knowledge to comprehend whether mentoring assisted practitioners to understand, navigate, and operate in the complex context of sustainability transitions. Hence, this thesis investigated the European project CIVITAS Handshake which is the first of its kind introducing mentoring relationships initiating such exchange between European cities that differ in their cycling planning experiences. The qualitative data analysis included semi-structured interviews of eight project participants, written answers of two informants of a project partner organization, and material produced during the project. The research suggests mentoring to be an assisting tool for practitioners and their planning activities on an individual basis. As these activities are situated in the complex context of sustainability transitions, mentoring also assisted in better understanding, navigating, and operating in this setting. Their participation in such interactions is socially significant as they are involved in decision-making in (mobility) planning toward more sustainability. However, the difficulty of tacit knowledge transfer and conversion, and the handling of learning individuals within organizations limit mentoring’s assistance. These constraints need future engagement and reflection.