Transmedia projects require organizations of different media design and production techniques and cultures to collaborate intensively with the goal to tell stories across different media, while creating a coherent user experiences across all media and in each individual component. Transmedia as a practice is a young field and no standards or widely adopted methods have yet evolved to create the connecting and overarching elements of such experiences. Predictability of cost and return on investment projections has not been achieved in most projects and the question remains, how self-sustaining in the long run Transmedia projects are (Franklin, 2012; Ibrus & Scolari, 2014). While there are questions around the profitability of Transmedia projects, at the same time there is a view that the potential is great to delight audiences with a single core narrative while having the opportunity to expand this across media into a multi-million Euro franchise (Ibrus & Scolari, 2014). While it is easy to add a companion website or a social media channel to a TV show, crafting an experience that fully enhances the story and that audiences will adopt is challenging and a field still in continuous development (Bernardo, 2014; Long, 2007). The goal of this research is to investigate how producers in Europe of different media backgrounds and from media organizations of different sizes collaborated during the Transmedia design process with the purpose of identifying which factors the producers see as critical for a successful Transmedia design. From the accounts the author deducts what the most needed elements for the further development of a Transmedia practice are to increase predictability and the intercompositional and integrative quality of the resulting experiences. The research is grounded in an analysis of current Transmedia definitions, the particularities of Transmedia design and an overview of types of organizations engaging in Transmedia collaborations. While scholarly literature provides a common viewpoint on what Transmedia experiences are and what kind of decisions need to be taken in the design for such experiences, the adoption of these practices and recommendations among the very different types of players in the field remains a question. With a constant change in audience behaviors and new technological options, the ‘how’ people collaborate and co-create becomes a more sustainable element to describe than individual concrete procedures. The research is a cross sectional qualitative research, combining an in depth literature review with semi-structured interviews with Transmedia producers from different types of media organizations (Bryman, 2012). The exploratory and descriptive purpose is to identify common patterns or themes in how Transmedia producers describe their personal experiences in Transmedia design through short narratives (Marshall & Rossmann, 2010). The sample was selected through the methods of purposeful selection and convenience based selection (Bryman, 2012). The Criteria for selection of the research participants was their experience as producers on complex European Transmedia initiatives, that tell stories across at least three media and that were the result of intensive interorganizational collaboration. Participants come form a variety of media backgrounds, i.e. TV, Film, Online / Digital, Game, Events, Print, Technology to capture the accounts of collaborations from different perspectives. After nine interviews the new interviews did not generate new codes and theoretical saturation was achieved. The accounts of success factors for Transmedia projects in the interviews focus on understanding the business value and on promoting a Transmedia culture and personal interactions on such projects. Four key themes emerged from the analysis of the transcripts: approaches for funding and project initiation, modes of decision-making, the importance of a Transmedia mindset and flexibility and continuous adaptation, and approaches and preferences for choosing methods. Practitioners recommend the practice focuses on the creation of business models and methods for co-creation rather than on standards and procedures for the design process. This assessment of the needs of the practice corresponds to the findings in the literature but goes further in the description of the criticality for co-location and co-creation across organizations. Business and partnership models between stakeholders in Transmedia design projects and the creation of measurement models stand the best chance to be widely adopted by the practice. Media managers deal with increasing production complexity resulting from the continued convergence of the media, technology and telecommunications industries. Understanding key success factors through direct insights and learning from practitioners of complex media co-creations from very different organizations provides ideas and inspiration around how to provide an environment that allows stories to come to life across media while at the same time focusing on business model design and strengthening the creative ecosystem.