Small, self-directed teams are central in agile development. This article investigates the effect of team- work quality on team performance, learning and work satisfaction in agile software teams, and whether this effect differs from that of traditional software teams. A survey was administered to 477 respondents from 71 agile software teams in 26 companies and analyzed using structural equation modeling. A posi- tive effect of teamwork quality on team performance was found when team members and team leaders rated team performance. In contrast, a negligible effect was found when product owners rated team per- formance. The effect of teamwork quality on team members ́learning and work satisfaction was strongly positive, but was only rated by the team members. Despite claims of the importance of teamwork in ag- ile teams, this study did not find teamwork quality to be higher than in a similar survey on traditional teams. The effect of teamwork quality on team performance was only marginally greater for the agile teams than for the traditional teams.