Urban green spaces are quite important in enhancing the environment and aesthetic quality of city life. Kisumu City, the study area, has been experiencing demographic, environmental, economic, socio-spatial and institutional challenges leading to loss of green spaces. The need to address these challenges are some aspects of concern within Kisumu City addressed by the study. Systems Theory was applied in the study and it focused on various components or sub-sectors which must function together in the urban environment. In this study therefore, Kisumu City is regarded as a system. The main problem addressed by the study was dysfunctional use of green spaces leading to their loss, aesthetic value and low environmental quality thus affecting ecotourism transformation. The broad objective of the study was to determine how urban green space planning can aid in transforming ecotourism in Kisumu City. Research design was explorative combining both quantitative and qualitative methods embedded with a case study. Content Analysis was used to examine the first objective: spatial planning interventions and their implications on conservation of urban green spaces and ecotourism. Spatiotemporal Analysis was used for the second objective to determine the effect of spatial change of urban green spaces on environmental quality and ecotourism. Principal Component Analysis was used to examine the third objective which focused on participatory innovative and alternative approaches to planning and managing urban green spaces to transform ecotourism. Data was both qualitative and quantitative and was collected through observation, interviews, questionnaires, photography, Remote Sensing and Geographic Positioning System (GPS). Qualitative research focused on site specific analysis of urban and peri-urban neighborhoods in Milimani and Nyalenda, respectively which were purposively sampled. The concept of densification was applied in selecting these case study areas. Systematic random sampling was applied when administering structured questionnaires to households within the study area. The hypothesis in this study was that temporal change significantly influenced loss of urban green spaces. The F value of 10.853 indicated that there was a significant relationship between change in time and change in area of the land classifications. Results showed that area under green has reduced by 19.9% from 2005 - 2014 leading to decrease in carbon sink resulting in increase in carbon footprint. This has led to low environmental quality which has a negative effect on ecotourism. The study projects that by the year 2030, without proper planning interventions, the city will lose all its urban green cover and create negative externalities on ecotourism. The research recommends the use of remote sensing for creating land-use inventory and monitoring systems. Citizen involvement in planning and management of urban green spaces is recommended because this will transform ecotourism in Kisumu City. The County Assembly needs to prepare a policy framework to support green city planning. In preparation of a green city plan, eight attributes (green planning and design, green open spaces, green waste, green water, green transportation, green energy, green building, green building and green community) identified by stakeholders must be integrated in planning. This will ensure that the city realizes benefits which will in turn lead to ecotourism transformation. In conclusion, there is need for capacity building for dealing with land management and green city planning issues.