The transition from school to university involves various challenges for the student body on an institutional, organizational, content-related and social level. The implementation of peer learning formats could address these challenges. Recent studies have already indicated positive effects on the processing of learning content, on motivational variables and on the learning success of university students. In the present study, a peer learning tutorial was implemented for first-year biology students. The relationships between participation in the tutorial and content processing, motivational variables, and the learning success of 178 biology students (M = 20.22 ± 2.74 years; 68.5% female) were examined by using multivariate and univariate analyses of variance. Data on the students' grades and participation as well as the teaching and learning conditions in the tutorial were collected. The results showed positive relationships between participation in the tutorial and content-related and motivational aspects. While the final secondary-school grade (Abitur) had an effect on the final exam grade, participation in the tutorial had also a relationship to the learning success of the biology students. Peer learning tutorials could therefore provide an effective support in the challenging introductory phase for university biology students.