Teacher knowledge building (TKB) is indispensable for teachers' continuing professional development (PD). However, studies on how teacher knowledge is built and how to facilitate this process are scarce. In this study, we critically reviewed the existing literature on TKB since 2016, focusing mainly on in-service teachers working in K-12 school settings. Thirty-six studies were identified and analysed regarding approaches to TKB, mechanisms underlying TKB, conditions facilitating TKB, and the measurement of TKB. On the basis of our findings, we propose a conceptual framework that firstly helps research community to understand and assess TKB and secondly provides promising approaches to design effective PD for teachers' knowledge building.