There is a growing interest in applying the psychological contract concept to the relationship between volunteers and nonprofit organizations. However, previous studies overlook certain elements of volunteers’ psychological contracts as they build on theory established with reference to paid employees. We argue that the inclusion of a value-based psychological contract type, next to transactional and relational types, enables a more thorough understanding of perceived mutual obligations between volunteers and nonprofit organizations. We use the critical incidents technique to map volunteers’ perceived (un)fulfilled obligations and find that volunteers perceive both fulfilled and unfulfilled value-based obligations. Moreover, we describe specific terms related to the mission and values of the organization reported by volunteers. We conclude that future psychological contract research needs to take this valuebased dimension into account, especially in volunteerism.