A social revolution is occurring in the way information is shared, knowledge is generated and innovation takes place over the Internet and there is renewed interest in the social concept of "community" to support online learning. This article describes action research conducted in the context of an eTwinning Learning Event (LE) that provides useful insights into how an online learning community can support the continuous professional development (CPD) of school teachers. Using the Community of Inquiry framework (Garrison "et?al.", 2000), it offers empirical evidence of how cognitive, social and teaching aspects impact competence development. It suggests that online learning communities offer an appropriate environment for teachers' intellectual and emotional reflection, characterised by trust, mutual respect and shared values centred on improving pupils' learning. It also suggests that the educational experience within such a community is significantly influenced by the tutor's design and moderation of activities aimed at fostering critical thinking. The article concludes that online learning communities offer a valuable alternative to traditional teacher training by supporting teachers to learn in the context of their everyday practice, whilst collaborating and reflecting on their experience with peers across regions and countries. Concerning the wider use of social networking for learning, it suggests that educators still have a valuable role to play in ensuring that collaboration leads to an effective educational experience. (Contains 4 figures and 1 table.)