Formative market research is the first step in developing evidence-based sanitation marketing programs. In Malawi, the design, implementation and evaluation of rural sanitation marketing programs has been limited. This study applied a mixed methodological approach to examine the dynamic interactions between the supply and demand of sanitation in three rural districts. The supply assessment identified an extremely limited range of latrine options. Sanitation suppliers reported very low household demand for their existing latrine options. An additional constraint reported by suppliers was householders' perception of a hardware subsidy for latrine construction. The demand assessment found a key constraint of constructing an unlined pit latrine was their short time-in-use (11–13 months). Householders expressed despondency at having to consistently rebuild collapsed, unlined pit latrines. For brick-lined latrines, a key barrier was affordability combined with an over-estimation of construction costs. Key motivations to construct brick-lined latrines included product attributes and social drivers. Wide variations in access to income and use of micro-finance organizations were recorded within and across the study sites. Formative market research is an iterative process from which new lines of investigation arise. This study provides information that will provide a foundation for the ongoing research, design, implementation and monitoring of rural sanitation marketing programs in Malawi.