This paper presents a review of urban slum and suburban sprawl situations across the world. The article is more descriptive in nature than analytical and has the objective of bringing out the interrelationships among urbanization, urban slums, suburban sprawls, and environmental sustainability. It begins by examining the concepts of urbanization, urban slums, suburban sprawl, safe cities, resilient cities, and sustainable cities. It then goes on to look at the causes and consequences of urban slums and suburban sprawl. Findings from the study revealed that slums and suburban sprawls are cogs in the wheel of safe, resilient, and sustainable cities. Therefore, the study recommends efficient urban management, the implementation of urban master plans, development control, and citizen participation in urban planning and management. Above all, for the achievement of safe, resilient, and sustainable cities, this study places more emphasis on the use of modern techniques of environmental monitoring and management.