Optimal use of products with recycled content (PwRC) has emerged as a targeted strategy to reduce construction and demolition (C&D) waste disposal and promote resource circularity in the building and construction sector. Within this context, the role of training in changing project designers’ attitudes and behaviour towards the use of PwRC is poorly investigated on a global scale. Hence, this study aims to develop a framework that shows how training can influence project designers’ attitudes and behaviour towards the optimal use of PwRC through two research questions: (a) what are the factors that influence to change the attitude and behaviour, (b) what are the existing theories and models that support the attitudes and behavioural changes, using a systematic literature review. The review found that changing attitudes and behaviour towards the optimal use of PwRC is influenced by psychological factors, although economic and sociological factors do also have an impact. Of these psychological factors, attitude, knowledge, perceived behaviour control, and subjective norms are more frequently examined. From the economic factors, economic benefits and from sociological factors, collaboration and communication are the primary considerations. The review also suggests that the theory of Planned Behaviour and the Extended Theory of Planned Behaviour are the most widely used theories in this respect. This study contributes to the knowledge development by proposing a seven-element training framework aiming to influence project designers’ attitudes and behavioural change towards the optimal use of PwRC. This is a foundation for further research on circular economy education for construction project designers.