Planning a public health initiative is both a science and an art. In the complex environment in which public health practitioners work, often under time constraints, where formal research literature is unavailable or uncertain, public health practitioners often draw upon 'other forms' of knowledge (e.g., tacit, or experiential, knowledge). Through use of focus groups and one-on-one interviews we aimed to gain a better understanding of how tacit knowledge is used to inform program initiatives in public health. This study was designed as a narrative inquiry, which is based on the assumption that we make sense of the world we live in by telling stories. Six public health units were purposively selected for maximum variation, based on geography and academic affiliation. Analysis revealed different ways in which tacit knowledge was used to plan the public health program or initiative, including discovering the opportunity, bringing a team together, and working out program details (such as partnering, funding). The findings of this study demonstrate that tacit knowledge is drawn upon, and embedded within, various stages of the process of program planning in public health. The results will be useful in guiding the development of future knowledge translation strategies for public health organizations and decision makers.