The growing popularity of online CALL professional development (PD) courses and programs has necessitated a more in-depth look into their design. For so doing, a qualitative case study was carried out to explore how project-based learning (PBL) contributes to six in-service teachers' CALL PD. Drawing on data obtained from technology-review projects and follow-up discussions, it was observed that the experience of review, reflection, and discussion enhanced participants' technological knowledge, along with their attention to the affordances and constraints of different tools, their application for materials development or selection, and CALL evaluation. The potential contribution of this study to PD research lies in the account of how inquiry-oriented projects can be defined into the design of a CALL PD. The integration strategies are applicable for online PD attempts across various contexts.