Purpose: Research into professional services firms that have successfully implemented and adopted Web 2.0 tools are still rare, with no widely known accepted methodologies or frameworks. The purpose of this case study is to investigate a medium-sized law firm that embarked on a KM programme that makes explicit use of emergent enterprise-based Web 2.0 tools. Design/methodology/approach: The overlying research methodology applied is action research, in particular participatory action research (PAR). The study draws on interviews with practitioners, consultants and knowledge workers and takes into consideration multiple stakeholder views and value conflicts. The project is part of a Knowledge Transfer Partnership between RPC LLP and Westminster Business School. Findings: Implementation of Web 2.0 tools in professional services requires the blending of a number of approaches to address the intrinsic tension between the open, participative behaviour and iterative development methodologies encouraged by social tools, and more traditional management styles and methods of developing IT solutions. Research limitations/implications: This article presents a single case study based on a law firm that, at the start of the research, was operating from a single location in London and at the time of writing has expanded to multiple locations, including overseas. There may be a limitation to implementing lessons learned and methodologies to larger organisations and organisations outside the legal sector. Originality/value: While many organisations are still attempting to understand how they can practically implement Web 2.0 tools, this case study presents findings from a law firm that has had an internal Web 2.0-based knowledge solution in place for over two years. The research also makes use of a KM maturity model in order to assess the impact of the Web 2.0 implementation.