This study aims to investigate how cross-sector collaborations facilitate social development stemming from weapon destruction programmes that address peacebuilding and the enhancing of human security (socio-economic and political security) in regions afflicted with armed violence. The authors aim to contribute to the literature by demonstrating the viability of previous theoretical methods on designing and implementing a cross-sector collaboration. The research entails a case-study of the HM initiative, a combined effort between three NGO’s from Sweden and El Salvador that involves melting down seized illegal weapons and repurposing them into valuable products for consumers, to ultimately bring about social development in the conflict-prone communities in El Salvador. Through interviews with the involved actors of the NGO’s and documentation of the initiative, this study focuses on the formation of a cross-sector collaboration, the building of internal and external legitimacy by NGO-business partnerships, and the practices that aim to assess public value creation. This study provides insights on antecedent and linking conditions for the formation of a cross-sector collaboration, collaborative processes and structures that foster trusting relationships with both partners and stakeholders, and an implemented accountability framework for the measurement of public value creation. The researchers close with a discussion of further suggestions for relevant research.