Constructivist approaches to instructional planning are now widely used for instructional planning, yet there is limited support for guiding students in this area. This paper presents a new tool, the Constructivist Planning Self- Reflective Tool (CPSRT), that supports pre-service teachers using a constructivist lesson planning approach. Grounded both in social cognitive and constructivist theoretical perspectives, the CPSRT facilitates self-monitoring, self-evaluation, and organization from a self-regulatory perspective, and cognitive flexibility from a constructivist perspective. Use of the CPSRT has implications for enhancing the training of pre-service and in-service teachers in a constructivist approach to instructional planning.