During 1999–2007, a labour-led but broad-based socio-economic rights movement, which focused on a pro-poor (and therefore highly popular) anti-fuel price hike message, persuaded and/or pressured Nigeria's federal legislature, the National Assembly, to: mediate between it and the Executive Branch of Government; take it seriously enough to lobby it repeatedly; re-orient its legislative processes; explicitly oppose virtually all of the Executive Branch's fuel price hikes; and reject key anti-labour provisions in a government bill. Yet the movement did not always succeed in its efforts to influence the National Assembly. This article maps, discusses, contextualises and analyses these generally remarkable developments. It also argues that while many factors combined to facilitate or militate against the movement's impact on legislative reasoning, process and action during the relevant period, this movement's ‘mass social movement’ character was the pivotal factor that afforded it the necessary leverage to exert considerable, if limited, influence on the National Assembly.