The proliferation of slum residential areas in cities in Sub Saharan Africa adversely affects the inhabitants through overcrowding and congestion, sub-standard housing development, disease prevalence, inadequate socio-economic infrastructures such as potable water supply, hygiene and sanitation facilities, wastes disposal schemes and drainage channels, the prevalence of crime and violence and environmental hazards such as floods and landslides. In Cameroon, slums continue to appear in cities and towns because of poor urban governance which fails to ensure effective and comprehensive city management strategy in order to prevent new slum neighbourhoods from emerging in the urban landscape and make existing ones more livable and sustainable. This study makes an appraisal of slum upgrading in Cameroonian cities and proffers a twin-track planning solution that will ensure an effective and comprehensive city management for urban sustainability. To do this, on-the-spot appraisals, field surveys and participatory appraisals were undertaken with individual slum households, quarter heads, municipal authorities, CIGs and NGOs working with slum dwellers and government ministries in charge with urban development for a period of twelve months. Analysis was done using descriptive techniques. Findings showed that the Participatory Slum Upgrading Programmes (PSUP) launched in 2008 and implemented by UN-Habitat which aims to improve the living conditions of slum dwellers is the current slum upgrading approach used in Cameroon. But an appraisal of the problems plaguing this approach shows that much still need to be done to assure adequate and decent affordable housing. Tenure security, financial difficulties, displacement/forced evictions, coordination of actors, follow-ups, determination of slum sites and their full coverage, the non-respect of building/construction norms during resettlement, trivial help from international donors, lack of technical expertise, government neglect and lack of political will and the socio-political unrest experienced in some regions of the country all constitute the main limiting factors to the success of the PSUP approach. These problems provide indicators for the need of an effective and comprehensive city management strategy beyond the PSUP approach which does not only improve the physical living conditions but also ameliorate the legal, economic, political and social wellbeing of the urban poor slum dwellers now and for the long term. For urban sustainability to be realised in Cameroonian cities, I proffer the City Development Strategy (CDS) framework as a twin-track holistic, proactive, forward-looking and citywide slum upgrading approach. The CDS is an effective and comprehensive city management approach which can simultaneously improve the living conditions of existing slums dwellers and prevent the formation of new ones amongst Cameroonian cities thereby contributing to meeting the SDG target on access to adequate and decent affordable housing and services by all.