Investment decisions are often delegated to financial intermediaries, yet beneficiaries rarely have meaningful influence over how their capital is invested. This creates a democratic deficit, especially when investment choices involve trade-offs between financial returns and social impact. We study how considered social preferences can be revealed in the field using deliberative democracy. Partnering with a large Dutch pension fund, we conduct two field experiments that combine a deliberative mini-public with a binding maxi-public vote. In the mini-public, 49 randomly selected members participate in a three-day, in-person process of structured peer deliberation and balanced expert briefings on sustainable investing. After deliberation, participants formulate and vote on recommendations for the pension board. Deliberation does not change how much financial return members are willing to sacrifice for sustainable investing. What changes is how members reason about the tradeoff. Deliberation increases self-reported investment knowledge and, consistent with this, participants shift from rule-based reasoning about principles toward a focus on concrete societal outcomes. Consequentialist views rise from 20.9% to 44.2%, while deontological views fall from 34.9% to 9.3%. Mini-public members recommend expanding impact investing. To test whether this reflects the broader membership, the board puts the question to a binding vote among all members, of which 13,619 participate, choosing between stopping, maintaining, or expanding impact investing under the explicit understanding that the outcome determines actual portfolio allocations. We communicate to participants that impact investing can lower participants’ pension payments at retirement but may have a positive environmental and social impact. Despite the financial trade-off, a clear plurality of 47.9% favors expansion, against only 15.6% who favor stopping. The board commits to increasing impact investments by 300 million to 1.2 billion euros. The mini-maxipublic elicits considered social preferences, translates them into consequential investment decisions, and builds support across political divides.