Striving towards sustainable event mobility in a developing country like Nigeria comes with challenges of existing transport problems, one of the threats to Nigeria’s population and commercial hubs. Its significance to the quality of life and well-being cannot be overstated as it affects Lagos residents. Lagos is a driver of diverse event audiences, rural–urban migration, and changes in urban mobility patterns. The path to delivering a sustainable event has contributed to domestic tourism and environmental pollution congestion. This study investigates large events and recommends sustainable mobility solutions for congestion-free events in a megacity, Nigeria. The study draws on an explanatory sequential mixed method research design and adopts a descriptive analysis to achieve the aim of the study. The finding revealed that large events in Lagos, Nigeria, are the most significant factor influencing the environment and road networks within the renowned cities during the event’s season. A colossal deficit is spotted between transport demand and supply due to low public transport coverage to reduce car dependency within the states. The study suggests that event organizers rely on informal transport modes (mini-buses, tricycles, and motorcycles) that are available and cover the city’s interconnected street roads. The interplay between formal and informal transport modes provides an organized, coexistent, and collaborative transport system. The findings of this study could assist transport planners, urban planners, and policymakers in Nigeria in identifying host areas with large events and proffering solutions to improve road usage and accessibility.