This research linked 47 Hong Kong and 35 Canadian teacher candidates in a new participatory culture project within the theoretical framework of new media literacies. This paper reports the qualitative data with quantitative descriptions of participants' social interactivity within the cross-border communities of practice. Besides the constraints of the designated online forum, findings relate that participants' engagement in the new participatory culture contributed to their knowledge- and awareness-building of harnessing online participation, new media technologies, and cultural/linguistic diversity in education. The paper concludes with implications of cultivating communities of practice buttressed by new media literacies for teacher professional development.