Globally urbanization is accelerating, especially within developing countries. This often results in vulnerable urban conditions with limited adaptive capacity to respond to climate change-induced hazards. In response, employing innovative solutions that lever existing unused and underutilized interstitial spaces within the urban fabric for climate change adaptation and mitigation purposes are needed. Essential to this strategy is a better understanding of the quantity and type of potentially available interstitial space. Using a mixed-method approach, this paper analysed the spatial and material condition of unused and underutilized interstitial spaces within a Southern African city. This study organizes these interstitial spaces according to programme, zoning, access, spatial definition, microclimatic characteristics and material use. It undertakes a quantitative assessment identifying seven specific interstitial space types, found in the total study area. Underutilized parking spaces and rooftop spaces are identified as the most prevalent space types with significant climate change adaptation and mitigation potential if appropriately retrofitted. Retrofitting these spaces are relatively effortless, and can ultimately improve the climate change resilience of these cities.