This study explores how the impact of a five ECTS professional development programme for university teachers affects their self-efficacy beliefs and teaching conceptions using a mixed methods approach. For the quantitative part of the study, participants completed pre-post surveys. From these surveys, we find that the programme led to an overall significant increase in reported self-efficacy beliefs. A sub-sample of ten participants participated in the qualitative part, which consists of four phases: three reflective assignments and an interview. Individual teachers demonstrate a dominant teaching conception in each phase and in almost half of the sub-sample it developed over time, moving from a teacher-centered to a more student-centered conception. When examining the development of self-efficacy and teaching conceptions collectively, three development groups are identified. Noteworthy is that teacher development is credited to the programme as a whole and not to a specific aspect.