This study examined boundary-crossing collaboration in a research-practice partnership (RPP) in initial teacher education in Germany, exploring improvements for the theory-practice link. This study aimed to evaluate this particular cooperation format, especially to identify success factors for RPPs and differences between actor groups. Characteristics examined include motivational factors, collaboration aspects, co-constructive knowledge acquisition, competence enhancement and satisfaction. The study drawed on a quantitative survey with 78 participants from four groups: school practitioners, researchers, teacher students, partners from extracurricular organizations. A one-way ANOVA was conducted, and a path model on effective relationships was calculated. Results revealed that RPPs are collaboration “on equal footing”; participation enables professional development in teaching, assessing, and innovation; sharing practical experiences is the dominant factor in knowledge co-construction and main driver of success; and motivation to participate is mainly regulated intrinsically. This study contributes to the international debate on RPPs and advocates their establishment in teacher education.