Effective faculty development workshops are essential to develop and sustain the quality of faculty's teaching. In an integrated problem-based curriculum, tutors expressed the needs to further develop their skills in facilitating students' content learning and small-group functioning. Based on the authors' prior observations that tutors' performance depends on their teaching context, a workshop was designed not only tailored to the tutors' needs but also organized within their respective teaching unit. The purposes of this study are (1) to evaluate whether this workshop is effective and improves tutors' teaching skills, and (2) to assess whether workshop effectiveness depends on tutors' performance before the workshop and on their teaching unit environment. Workshop effectiveness was assessed using (a) tutors' perception of workshop usefulness and of their improvement in tutorial skills, and (b) students' ratings of tutor performance before and after the workshop. In addition, an analysis of variance model was designed to analyse how tutors' performance before the workshop and their teaching unit influence workshop effectiveness. Tutors judged the workshop as helpful in providing them with new teaching strategies and reported having improved their tutorial skills. Workshop attendance enhanced students' ratings of tutors' knowledge of problem content and ability to guide their learning. This improvement was also long-lasting. The workshop effect on tutor performance was relative: it varied across teaching units and was higher for tutors with low scores before the workshop. A workshop tailored to tutors' needs and adapted to their teaching unit improves their tutorial skills. Its effectiveness is, however, influenced by tutors' level of performance before the workshop and by the environment of their teaching unit. Thus, to be efficient, the design of a workshop should consider not only individual tutors' needs, but also the background of their teaching units, with special attention to their internal organization and tutor group functioning.