This article contributes to the debates over the development of solidarity among a fragmented workforce by discussing the case of a strike in which the technicians and contractors at Movistar in Spain were involved. The strike involved employees and self-employed workers working for different contractors. The results highlight that ‘spontaneous’ mobilizations can help to develop a collective identity in fragmented employment systems. More concretely, they show that the lack of involvement of unions at the beginning of the strike helped to generate an identity involving all workers that was not based on occupational or contractual status. However, the findings also highlight that the later involvement of independent unions, which respected the assembling of workers as a space of decision, was key to the sustainment of the collective identity. Furthermore, the results show that mobilizing can be a strong organizing tool in contexts characterized by weak institutional regulation, fragmentation and precarious working conditions.