The health security planning process transforms recommendations from various evaluations into priority actions to strengthen countries' capacity for emergency preparedness using the One Health approach. Although the World Health Organization (WHO) has developed many tools to facilitate the planning process of a National Action Plan for Health Security (NAPHS) across the various components, a series of multisectoral workshops is still needed to complete the process. In this article, we report on the process of developing Cameroon's NAPHS and propose an innovative solution to improve the process. The NAPHS development process was conducted from May to December 2018. The WHO NAPHS framework, adapted to the local context, guided the process. The WHO planning matrix was used to plan activities and the WHO NAPHS costing tool was used to facilitate the costing exercise. A total of 84 Joint External Evaluation recommendations were translated into activities included in Cameroon's NAPHS. Among these activities, the majority (56%) were of medium priority. The total cost of a 5-year NAPHS was US$87,668,356, with almost half (49%) of the budget allocated to activities in the "Prevent" category and more than a third (35%) allocated to the "Detect" category. The top 3 cost drivers were immunization (22%), the national laboratory system (21%), and antimicrobial resistance (16%). The NAPHS informed policymakers of planned activities and funding needs to fast-track the development of health security capacities. Running gaps in funding will be addressed during a resource mapping exercise. To improve the overall planning process, a web-based support solution, where stakeholders select from a menu of recommendations from the Joint External Evaluation to develop a NAPHS, should be developed to improve the NAPHS development process.