Emerging from the concept of & One Medicine & developed by Dr. Calvin Schwabe, the term & One Health & began its conceptualization more than 20 years ago with the SARS and H5N1 epidemics and the formulation of the 12 Manhattan Principles. Since then, numerous researchers and organizations have developed opinions and created diagrams to define One Health. The Tripartite, later expanding to the Quadripartite, followed this trend and established the OHHLEP (One Health High Level Expert Panel), which officially defined One Health in 2023. They also developed the Theory of Change forOne Health, which is used in the Quadripartite OH Joint Plan of Action. Unfortunately, despite these definitions and guidelines, the operationalization of One Health still faces various challenges. The focus on zoonotic diseases shows the misunderstandings and misinterpretation of the concept among funders, governments, and researchers. Thus, One Health actors still report two main barriers to operationalisation: the work in silos, often excluding ecosystem health, and the lack of institutionalisation. In Africa, however, some countries, such as Kenya, Senegal, Rwanda, and Cameroon, have already institutionalized One Health, while others have begun the process with the assistance of projects like COHESA (Capacitating One Health in Eastern and Southern Africa) and/or the Quadripartite. As the institutional barriers have been gradually overcome, the conceptualization and operationalization of ecosystem health within the One Health approach remain the next challenge.