Horizontal logistics collaboration (HLC) practices have gained much attention in recent years as innovative ways for companies to improve their performance. However, literature does not reveal which factors influence the success or failure of HLC, especially in agri-food supply chains (AFSCs) in developing countries. Therefore, this paper aims to investigate HLC in the context of AFSCs in Morocco as a case of a developing country. First, a literature review is performed to develop a conceptual model for HLC considering AFSCs characteristics. Then, in-depth case studies are conducted in Morocco to refine the conceptual model based on insights from real collaboration experiences. The results show that collaboration outcomes are influenced by operational collaborative activities through the mediation of relational elements. The operational collaborative activities are impacted by AFSCs’ characteristics, such as products specific handling conditions. Furthermore, the research shows that local cultural factors influence the development of trust in the relationship.