Abstract: Although Cross-Classroom Collaborative Project-Based Learning (C3PjBL) has many potential benefits, teachers engaging in it might need support due to challenges they face, such as, time constraints. This paper argues for the use of online teacher learning communities (Online TLCs) as a support mechanism for these teachers and uses a C3PjBL case study, from the literature, to provide an example of the proposed approach. Using this method, subcommunities are formed using C3PjBL learner-groups, and a project-group, encapsulating these learner-groups, forms the Online TLC. Teachers benefit from these communities through the asking and answering of questions, the giving and receiving of feedback, reflecting and the sharing of resources. This proposal represents a significant integration of C3PjBL and Online TLCs for enhanced teaching and learning quality and capacity building.