This article proposes an auction model where two firms compete for obtaining the license for a public project and an auctioneer acting as a public official representing the political power, decides the winner of the contest. Players as firms face a social dilemma in the sense that the higher is the bribe offered, the higher would be the willingness of a pure monetary maximizer public official to give her the license. However, it implies inducing a cost of reducing all players’ payoffs as far as our model includes an endogenous externality, which depends on bribe. All players’ payoffs decrease with the bribe (and increase with higher quality). We find that the presence of bribe aversion in either the officials’ or the firms’ utility function shifts equilibrium towards more pro-social behavior. When the quality and bribe-bid strategy space
is discrete, multiple equilibria emerge including more pro-social bids than would be predicted under a continuous strategy space
