Purpose: The literature has shown great interest in open innovation, and also discussed its degree of openness based on, for example, the number of parties involved. Less is known, however, about what makes open innovation processes work. This paper describes and discusses the importance of trust in open innovation, and specifically focuses on a start-up company’s open innovation processes with collaboration parties. The paper points out how a lack of trust antecedents may disable such open innovation processes.

Design/methodology/approach: The empirical part of the paper consists of a case study on a medical-technology start-up. Interviews and analyses of secondary sources made up the main data capturing methods. Each collaboration between the start-up and another party was analysed through three trust antecedents: contractual, competence-based, and goodwill.

Findings: The paper shows how either party may have chosen to discontinue the collaboration based on the lack of competence or goodwill antecedents to trust. Specifically, the case indicates how the start-up discontinued the collaborations based on a perceived lack of goodwill, while the collaboration parties based their decisions on competence deficits by the start-up.

Originality/value: The paper contributes to previous research through describing open innovation related to start-ups, and introducing trust antecedents as prerequisites for open innovation. To the literature on trust, trust mutuality makes a research contribution.