Professional development plans (PDPs) have recently been introduced in Dutch schools to support teachers' professional development. However, teachers' beliefs regarding the use of PDPs have not been systematically researched, whereas research on the use of PDPs indicates that the implementation is not always successful and depends on how use is perceived by users. Some teachers may doubt the usefulness and purpose of a PDP, and this might influence their reactions to its introduction. Using Fishbein and Ajzen's theory of planned behaviour, the current study explored teachers' characteristics (such as age and years of experience in education) and their beliefs about intention to use a PDP. Clusters of teachers with similar characteristics and beliefs were identified to permit the design of interventions specific to each cluster. Semi-structured interviews were conducted to reveal these beliefs and characteristics for a sample of 41 teachers working in schools where using a PDP was mandatory. The results showed that most teachers had a positive attitude towards using a PDP. However, because using a PDP was mandatory, they felt pressured to produce one. Moreover, it was not a priority. This was because of their high workload. The present study contributes to the literature by adding knowledge of teachers' beliefs about the use of PDPs. This knowledge may help the PDP to become a more effective device in promoting teachers' professional development.