Urban mobility systems increasingly operate under conditions of uncertainty, disruption, and socio-technical transformation. Drawing on empirical evidence from the AntifragiCity citizens’ forums conducted in Bratislava, Larissa, and Thessaloniki, this paper explores what deliberative engagement can reveal about the social acceptability of urban mobility interventions in the context of antifragile city design. The study highlights how deliberative engagement can uncover socially grounded understandings of mobility transitions through collective reasoning, reflection, negotiation, and the formulation of recommendations. The findings further suggest that social acceptability is dynamic rather than fixed, extending beyond simple categories of support or opposition. Ultimately, the forums highlight the value of deliberative engagement for informing more adaptive, socially responsive, and publicly legitimate urban mobility strategies.