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 participants' engagement in the new participatory culture contributed to their knowledge- and awareness-building of harnessing online participation, new media technologies, and cultural and linguistic diversity in education. The paper concludes with implications of cultivating communities of practice buttressed by new media literacies for teacher professional development.