This article examines whether a mixture of virtual and real-life interaction--in contrast to purely virtual interaction--among some members of online communities for teachers is beneficial for all teachers' professional development in the whole community. Earlier research indicated that blended communities tend to face fewer trust and free rider problems. This study continues this stream of research by examining whether blended communities provide more practical benefits to teachers, both in terms of perceived improvements to their teaching capabilities as well as for their substantial understanding of their core topic. In addition, it is tested whether blended communities provide more information about vacancies, as teachers' mobility is regarded as too low in the EU. The analysis uses survey data from 26 online communities for secondary education teachers in The Netherlands. The communities are part of a virtual organization that hosts communities for teachers' professional development. The findings indeed show beneficial effects of blended communities. Moreover, the results modify earlier claims about the integration of online communication with offline interaction by showing that complete integration is unnecessary. This facilitates a scaling up of the use of online communities for teachers' professional development. (Contains 9 tables.)