This study aimed to examine the historical loss of public open spaces in Nairobi City, assess the residents’ awareness of the importance of the resource and determine the collaborative planning and governance approaches used for delivery of sustainable open spaces. The study design employed the positivist and interpretive approaches. Population sampling was based on the Yamane scientific formula (n=400) from a target population of 4.247 million, applied through random sampling and purposefully sampled key respondents (n=20). The applied research instruments were general and key respondent questionnaires, face-to-face interviews, participant observation and review of documents and maps. The study’s unit of analysis was aggregate group scores displayed in percentages, tables, histograms, bar and pie charts. The study results revealed serious loss of public open spaces, residents’ awareness of open space benefits and absence of collaborative planning and governance practices. The study recommended new governance structures, higher status for urban planning and sustainable open spaces delivery based on pertinent frameworks achieved through collaborative governance approaches.