This study examined the role of waste management authorities in promoting public awareness of municipal solid waste management (MSWM) through the lens of the expansion diffusion theory (EDT). EDT emphasizes the spread of new ideas and practices within a society through various communication channels and distinct individuals within each system. We employed a mixed-method approach using 116 survey responses from Lagos residents and five semi-structured in-depth interviews. Our findings reveal the need for a more structured approach to create public awareness of MSWM, considering the distinct groups of residents in Lagos and their responses to innovation and knowledge diffusion. We propose four pillars on which waste management authorities in developing countries can sustain their MSWM awareness campaigns, as well as an awareness campaign strategy flowchart. Our findings add to the expanding body of research on public awareness and participation in MSWM, emphasizing the critical role that waste management authorities can play in fostering sustainable waste management awareness and practices.