There is a need for empirically based research on social and ethical challenges related to informed consent processes, particularly in studies focusing on adolescent sexual and reproductive health. In a pilot study of a school-based pregnancy prevention intervention in rural Zambia, the majority of the guardians who were asked to consent to their daughters’ participation, refused. In this paper we explore the reasons behind the low participation in the pilot with particular attention to challenges related to the community engagement and (...) informed consent process. The pilot was implemented in two schools and examined the acceptability of a package of interventions including economic support to families to keep their girls in school, pocket money for girls, youth club meetings on reproductive health, and community meetings to sensitize the community. Focus group discussions were conducted with girls who participated in the pilot, boys in their class and with parents. Individual semi-structured interviews were conducted with teachers, peer educators and community health workers involved in the coordination of the intervention as well as with religious and traditional leaders. Data were analyzed through thematic analysis. The findings indicate that inadequate use of recognized community communication channels during the community engagement process and dissemination of information about the pilot resulted in limited understanding of the pilot concept by the community. This surfaced through uncertainty and fear that the intervention may result in loss of control over daughters, worries about why money was provided unconditionally to girls, and suspicion of links to satanism. The sense of insecurity appeared to be exacerbated by low literacy levels, poverty, fear of loss of bride wealth, perceived disregard for local perceptions of social status, and scanty trust in the actors implementing the pilot. Inadequate use of locally appropriate channels in the dissemination of information created room for interpretation and facilitated development of mistrust, undermining the conditions for community engagement and actual informed consent. A key lesson learnt is the importance of taking seriously the complexity of local values and structures that may impact people’s capability to consent or not consent to a study in an informed manner. (shrink)