In Ghana, unplanned and spontaneous urbanization has trapped many in slum dwellings with its attendant poverty, insecurity, and poor housing and general environmental conditions. Slum dwellers' choices of livelihood activities are restricted under various socioeconomic and planning constraints. Using mixed methods, this paper explored the conditions under which slum dwellers can maximize the prospects of their environment and minimize the challenges therein. The findings indicate that slum dwellers have diversity of livelihood assets and potentials, yet limited access to planned adaptation remains a main challenge. Many dwellers result to autonomous "supplementary occupations" to cope with the challenges of urbanization. It is therefore imperative to redefine the mandate of urban planning, as a response to spontaneous urbanization, and to develop a tool for sustainable livelihood at the local level.