Background: Despite a vast literature on collaborative learning (CL), there is little research on preparing students to work collaboratively. Aims: This two-phase evaluation investigated whether team-skills training could enhance the performance of collaborative groups through the introduction of a team development programme to a group-based undergraduate key-skills unit. Sample: Phase 1 compared two consecutive cohorts of second-year students, Cohort 1 (N = 94) who received no preparation, and Cohort 2 (N = 113) who received team-skills training. Phase 2 added Cohort 3 (N = 88), who also received team-skills training, to extend the analysis. Method: In Phase 1, students in both Cohorts 1 and 2 worked on a series of curriculum based key-skill tasks across two semesters. Students worked in one group in Semester 1 and were then formed into new groups for Semester 2. Effects of the training were measured by student group marks and key-skill ratings. Results: Marks and key-skill ratings were significantly higher for the trained cohort in Semester 1 (p less than 0.01). However, in Semester 2 performance reduced for the trained cohort in comparison to Semester 1. To explore this further, Phase 2 of the study evaluated Cohort 3, where after training, collaborative groups remained intact throughout the academic year. Results for Cohort 3 showed no attenuation of performance effects in Semester 2. Conclusions: Phase 1 results support the use of team-skills training to enhance CL group performance. The findings for Phase 2 suggest that these benefits may be lost if training groups are disrupted.