Collaborative governance networks are increasingly put in place in the public administration to enhance interactions between a diversity of actors (e.g., civil servants, companies or citizens) in a more horizontal setting, in the hope that cross-cutting public policies (e.g., climate policies) gain coherence and become more innovative. To do so, collective learning, defined as the broadened and mutual understanding of public issues arising out of repeated social interactions, is critical but not spontaneous. How does diversity lead to collaborative learning in context of collaborative networks?To address this research question, we look at two collaborative networks occurring in the administration of the city of Schaerbeek (Belgium),with questionnaire items and semi-structured interviews, as well as a social network analysis. Collective learning is innovatively measured with mental models’ elicitation. The findings highlight the importance of the subjective appreciation of diversity as well as informal social interactions to favor collective learning.It also confirms the potential of collaborative networks to foster innovative ideas.These results provide a better understanding of collective learning in administrative collaborative networks, as well as the interactions between the factors of collective learning.