Achieving the goal of sustainability requires understanding and management of unprecedented and interconnected challenges. A transdisciplinary approach is a key component of sustainability science. However, there are considerable barriers to implementing transdisciplinary projects. We undertake a mixed quantitative and qualitative analysis of peer-reviewed sustainability science studies where the transdisciplinary approach has been applied. We assess the growth and scientific impact of transdisciplinary sustainability research, the methods used and how three key characteristics of transdisciplinarity research-process phases, knowledge types and the intensity of involvement of practitioners-are implemented. While transdisciplinary research is growing there is no common glossary, no focused communication platform and no commonly shared research framework. Transdisciplinary research utilizes a broad, but not clearly defined, set of methods for knowledge production. While the intensity of practitioner involvement varied within the case studies analyzed, very few realized empowerment. Based on our review of transdisciplinary case study papers we conclude that transdisciplinary research must be clearly framed, including the use of a common terminology and the development of a broad suite of appropriate methods. Despite the challenges highlighted here, science needs to move beyond classical disciplinary approaches and should consider interdisciplinary work that engages with practitioners to achieve sustainable transitions.