This paper attempts to measure the extent of impact of the City of Cape Town’s open government data initiative, which has been operational since 2013. Given the relative scarcity of impact measurement frameworks, a framework is adapted from that of Verhulst and Young [1], as well as the Social Return on Investment (SROI) framework suggested by Stuermer and Dapp [2]. The idea is to trace the developments resultant from the use of open data from various sources, mainly the City of Cape Town’s open data portal. Several activities and developments are identified and classified under a classification scheme adapted from development pathways relevant to a developing country context. The development pathways are identified from literature. After the developments are traced, critical impact analysis is carried out using the SROI framework. The findings suggest that although there are some indications of impact, such impact is only confined to groups with specialised and specific interest in various types of open data. Additionally, awareness of the existence of open data-sets is also minimal, which significantly decreases the likelihood of use, ergo, impact. Policy suggestions to increase likelihood of use and impact are then presented.