The professional development of teachers in China takes place, to a large extent, in Teaching Research Groups (TRG) that exist in all schools. Though there are diverse models of TRG activities, these might, on the surface, appear to resemble forms of Action Research (AR) or include elements that might resemble AR. In conducting a Lesson Design Study (LDS) with a TRG in Shanghai, we encountered the specific challenge of what might be the interconnectedness and differences between AR and our LDS. To address this issue, we applied a research-informed depiction of the distinguishing characteristics of AR to our LDS. Based on this analysis, we found that (1) in contrast to the depiction of AR that encompasses a choice of methods, our LDS follows a specific 'design research' methodology, (2) whereas the depiction of AR is simultaneously directed towards teacher self-change and restructuring the organisation or institution within which the teacher works, LDS concerns more than the practical questions in one local social context and aims to tackle bigger questions across the social contexts in the subject research field, and (3) whereas in the depiction of AR, teachers engage in a process of authentic collaboration with other teachers seeking to improve their practices, in the LDS community the external researchers and expert teachers play other roles in the TRG. Even though there may be differences between the depiction of AR and our LDS, the interconnectedness is important in that both AR and our LDS contribute directly to school-based teacher professional development.