This paper examines what motivates the participation of African slum(1) dwellers in urban social movement activities. This issue is analyzed through a case study of grassroots mobilization around evictions in Kurasini ward, Dar es Salaam, Tanzania. The paper uses an analytic narrative approach to account for patterns in participatory behaviour, drawing on both quantitative and qualitative data gathered through interviews with 81 slum dwellers. The study shows that, contrary to the expectations of movement leaders, property owners were significantly more likely than renters to participate in a risky and time-consuming mobilization effort. The study identifies three factors that favoured owner participation: the nature of expected payoffs from participation; greater belief in their efficacy of action; and greater connection to place.