Effective corporate governance requires mechanisms that allow shareholders to influence corporate decisions. This paper investigates the use of shareholder proposals, an increasingly prominent governance mechanism, by labor unions. Activist union pension funds are subject to cross-pressures: they wish to increase fund returns to help beneficiaries but also to aid current union workers. We show theoretically that shareholder proposals can be used as bargaining chips in contract negotiations. Empirically, we use variation in the expiration of collective bargaining agreements to identify exogenous changes in the value of making proposals. We find that during contract negotiation years, unions increase the number of proposals they make by about one-quarter (and by about two-thirds during contentious negotiations), and change the subject of proposals to focus on matters personally costly to managers. We do not find similar changes in proposal behavior by nonunion shareholders. Opportunistic union proposals are also associated with better wage agreements for the union. The evidence suggests that some union proposals are intended to influence collective bargaining outcomes rather than maximize shareholder value, and that increasing proposal rights will not necessarily help shareholders at large if some shareholders use those rights to advance their private interests.