Practices such as formal focused professional dialogue groups, coaching conversations, mentoring conversations and professional learning staff meetings have been taken up in schools and pre-schools as part of long-term action research and development activities to improve the learning and teaching practices. The development of relational trust has long been described in the literature as pivotal for the ongoing "success" of such research and development in sites. In this article, we attempt to re-characterise relational trust as it is accounted for by participants in action research. We present data from a cross-nation study of middle leaders from Australian primary schools and Swedish pre-schools. Middle leaders are those teachers who "lead across"; they have both an acknowledged position of leadership or responsibility for the practice development of colleagues and a significant teaching role. The larger study examined the practices of middle leaders; and in this article we draw on interview data from one of the case-study sites that illustrate how colleagues in schools recognise the role middle leaders have for facilitating action research and teaching development. This article specifically presents excerpts from semi-structured interviews with 25 teachers, three principals, three executive teachers and three district consultants. Interviewees described how nourishing a culture of relational trust and mutual respect are critical features in the change endeavour. For them, the practices of the middle leader who facilitated the action research were instrumental in developing trust for teacher development. Analysis of participant accounts revealed five dimensions of trust: interpersonal trust, interactional trust, intersubjective trust, intellectual trust, and pragmatic trust.