Coping with intergenerational conflicts is one of the fundamental keys to building a sustainable society. However, current decision-making systems tend to be inclined towards the preferences of present generations, simply because future generations do not yet exist and therefore cannot participate in present-day negotiating processes. In this paper, with an aim towards reconciling possible intergenerational conflicts, we present the first attempt at creating a participatory intergenerational deliberation practice by creating “imaginary future generation” groups to represent future generations and negotiate with present-generation groups regarding future visions and associated decision making. To accomplish this, a series of workshops were organized in a local municipality in Japan in which participating imaginary future-generation groups and present-generation groups first deliberated separately, and then worked together, to form a consensus over prioritizing policy measures associated with their separate visions of the municipality in 2060. We then analyzed deliberation and consensus-building processes used and observed a stark contrast in deliberation styles and priorities between the groups. For example, imaginary future-generation-group measures were primarily characterized by utilizing existing local resources, while the present-generation groups aimed more at solving current problems. Notably, the consensus-building processes resulted in choosing more than half of the measures originally proposed by the imaginary future-generation groups, thereby indicating that decision-making preferences had shifted to future generations. We contend that our approach, which is based on introducing imaginary future-generation groups as stakeholders, could provide indicators towards coping with intergenerational conflicts via present-day decision-making processes.