PhD trajectories are important to universities, as these contribute to the increase in knowledge and output. Therefore, they aim to decrease the completion time and dropout.This article reports on our survey amongst PhD candidates and supervisors of the Graduate School CAPHRI, Maastricht University, The Netherlands. We investigated interpersonal aspects of coaching and (implicit) assumptions on skills and competences.Both groups consider personality, knowledge, skills, communication and coaching the major factors contributing to a successful PhD trajectory. PhD candidates consider responsiveness and respectful, good-quality feedback by supervisors important and suggest regular assessment of their performance. Supervisors consider flexibility, openness for feedback, taking initiative and being a team-player as good qualities for PhDs. Supervisors indicate struggling with offering support versus independence during different stages of the PhD trajectory.The study shows that a good match between PhDs and supervisors is essential for a successful PhD trajectory, and we advise that both discuss and formally agree upon mutual expectations and responsibilities within the project. We advocate that Graduate Schools foster an open and safe learning environment, organise meetings where supervisors can share experiences to learn from one another, provide contacts for advice and support and involvement of HR during the selection process.