PurposeThis paper aims to study the results of open innovation initiatives in Spain under the lockdown during the first stages of the COVID-19 crisis. Based on the most recent literature on open innovation in the public sector, this paper explores the following research questions, namely, what are the key features of collaborative governance processes that guided open innovation initiatives in the Spanish public sector during the COVID-19 crises? How open public innovation cases generated public value to the society during the COVID-19 crises in Spain?Design/methodology/approachThe study is based on two in-depth case studies of open innovation in the public sector: the collaborative platform Frena la Curva and the hackathon Vence al Virus, both launched during the first moments of the COVID-19 crisis. The methodology is based on 13 semi-structured interviews, content observation and documentary analysis. The data were interpreted according to the dimensions described in the analytical framework: descriptive dimensions of both initiatives but also their degree of elaboration, incentives and objectives, characteristics of governance and collaboration between actors and challenges for the accountability processes; and finally, their procedural legitimacy, considering the COVID-19 crisis context.FindingsThe results of the study show that citizens have played a key role during the hardest stage of the crisis, collaborating with governments and advancing their innovative capabilities, mostly in the digital sphere. The analysis also identified different outcomes, including the improvement of citizen’s involvement, deliberation practices or network building. Besides, this paper has identified some limitations and barriers to open innovation and collaborative governance processes in terms of accountability and legitimacy of these initiatives. Here, their contribution was constrained by the emerging stage of implementation and by the unique circumstances of the lockdown under the COVID-19 crisis.Research limitations/implicationsFuture advancements of open innovation initiatives to consolidate collaborative governance processes will need further exploration. Although this paper diversified the contacts and the data collection in the fieldwork to avoid social biases, the results of the interviews might reflect very positive outcomes. Despite the case studies that took place during the COVID-19 crisis and their planned actions to maintain their existence, the post-crisis analysis will be needed to assess the impact of these open innovation cases in collaborative governance structures.Practical implicationsOpen innovation is an emerging narrative and practice in the public sector requiring time and energy from public officials and managers. The study also highlighted the problem of how to legitimate open innovation cases in the public sector and the implications for their institutionalization. Public managers involved in these types of initiatives need to keep the momentum both inside and outside their organizations. Regarding the utilization of information and communications technologies (ICTs), open innovation processes do not need technology to develop their full potential, whereas the COVID-19 crisis and the ongoing digitalization of work settings, accessibility, etc., could transform ICTs into a critical tool for public managers leading innovation initiatives within their organizations.Social implicationsThe social implications of this paper are manifold. This study provides evidence of one of the future avenues of public management: open innovation. New avenues for the involvement and collaboration of citizens with public authorities are another social implication pinpointed by this paper. Democratic legitimacy and procedural accountability are assessed using the open innovation case studies during the COVID-19 crisis. Finally, transforming governments using collaborative platforms deserves social oversight understanding if they really contribute to build trust in political institutions.Originality/valueDespite their differences, both Frena la Curva and Vence al Virus demonstrated the potential and limitations of public innovation and collaborative governance to cope with an unprecedented crisis such as the COVID-19. The special features of this emergency, including the long period of confinement, posed challenges and also opportunities to develop these initiatives: as several interviewees stated, these projects helped to channel the civic energy to co-produce solutions in collaboration with a wide range of actors. Data allow us to identify the key features of collaborative governance that guided open innovation initiatives in the Spanish public sector during the COVID-19 crisis.