Health Impact Assessments (HIA), promoted by WHO, are generally presented as a process supporting decision-making in favor of health. HIA differs from other forms of policy assessments as it relies on core values among which democracy, equity and sustainable development. It is also characterized by a cross-sectional approach based on the diversity of health determinants that are taken into account. Beyond decision-making, we explored the capacity of the HIA process to generate a collective (social) learning among participants. We questioned its ability to facilitate the emergence of a common culture on health, its determinants, and urban planning. Here we report on our experience of an HIA conducted on a large urban project in the west of Paris. We pursued an open approach allowing municipal agents to actively participate in the process, and learn about the project in general, using health as a new lens for the appraisal. The participants, originating from several departments, were involved in collective working sessions. Their contribution was sought for the elaboration of a set of assessment criteria, linking health determinants with the major issues of sustainable development, then focusing on the assessment of the urban project through a global deliberation. At the end of the HIA process, participants were asked to respond to a survey regarding their opinion on the whole process and the benefits they perceived. Responses seem in support of the relevance of our approach, favoring the participants’ engagement and allowing them to widen their perspectives, beyond their usual field of competences. The HIA process, which included municipal agents, and the discussion that was generated throughout, were perceived as a means to objectivize and federate opinions on issues that are not, or seldom, considered explicitly by urban planners.