This study explores the notion of learner participation within the context of online language learning in virtual world platforms. Participation is discussed as learner interaction in the target language with reference, in particular, to Breen (2001) and Lantolf (2000) and as online learner activity as discussed by Bento and Schuster (2003) and Hrastinski (2007). In addition, the study builds more specifically on existing research into learner participation in virtual worlds by Deutschmann, Panichi and Molka-Danielsen (2009) and Peterson (2010). Data was collected through a case study of a Business English course within a European telecollaboration project at tertiary level. The course at the centre of the case study comes under the umbrella of the EU-funded Euroversity Network (www.euroversity.eu). The study makes use of Reflexivity (e.g. Alvesson and Sköldberg, 2009) and Exploratory Practice as its core methodological approach to the building of the case. The virtual world data is analysed from a multimodal perspective within CMCL (e.g. Lamy, 2004) and makes use of visualisation (Mason, 2002) as the primary analytical tool. The study provides an expanded definition of learner participation which reflects the learning dynamics of virtual worlds within the specific teaching and learning context. The study evaluates the role played by designer beliefs in determining learner participatory outcomes and makes recommendations for teaching and future course design. The study also illustrates the use of virtual world platforms as a research tool.