PurposeThe purpose of this work is to study the relationships of trust in a local agri-food supply chain in Southern Brazil. In an unsustainable context, where the number of mariculturists is decreasing, the authors seek to identify what the factors are and how they contribute to this problem, as well as find solutions aimed at the sustainability of that chain.Design/methodology/approachThe authors carried out qualitative research with 15 semi-structured interviews that took place in the year 2021. The thematic analysis of the results applied the IRAMUTEQ software and the assessment of the narratives was guided by prior thematic analysis.FindingsThe supply chain under investigation requires better organisation. Communication and interpersonal trust proved important in the relationship between producers and control bodies. The university, as a seed supplier, needs predictability and efficiency to convey inter-organisational trust. Informal relationships are interpersonal and extremely trust-based and inter-organisational trust increases the performance of establishments and promotes the development of innovative structures. Furthermore, in crisis periods interpersonal trust increases.Practical implicationsThe results allow policymakers to plan better their actions and build more effective tactics in order to reach sustainable development. This work is also important for stakeholders and managers, as it guides improvements in management, governance and sustainability of agri-food supply chains.Originality/valueAn unprecedented research was done on the studied supply chain, knowing the relationships of trust among them, identifying peculiar partnerships and recognising some constructs and outcomes of trust.