Social media is a veritable tool for ensuring environmental accountability. This paper explores the veracity of this position in Lagos State, Nigeria’s most populous subnational unit. Given the conurbation’s over 20 million population, the rate of poor environmental behaviour, such as indiscriminate waste dumping, noise pollution, industrial and domestic pollution, deforestation and land reclamation, amongothers, is debilitating. With social media’s ubiquitous mediation of everyday life, this paper notes that it has assumed a serious accountability tool in state’s environmental management space. This paper is based on the mixed-method research design involving a quantitative survey of 100 respondents and an interview of 10 participants, and the theoretical blending of the assumptions of Metropocentric and agenda-setting theories. The paper notes many instances of netizens reporting poor environmental behaviour over social media and the government’s interaction with residents over them. It argues that this aligns with online campaigns, such as #PickThatTrash on X (formerly Twitter). These findings are, however, dampened by the fact that the bulk of social media users have low engagement with environmental content. The paper recommends heightened social media advocacy for the environment to bolsterits environmental accountability roles in the state.