One's own emotions may influence others' behavior in a given social interaction. If one believes this, s/he has an incentive to game emotions - to strategically conceal a current emotion or display a non-experienced emotion - in an attempt to influence her/his counterpart. In a series of three experiments, we show that people deliberately conceal (experiment 1) or misrepresent (experiments 2 and 3) their emotional state in a negotiation setting. When given the opportunity to either hide or express their current emotions before playing an ultimatum game, receivers who have reported low (vs. high) level of anger are more likely to conceal their emotion right before the proposers decide on the division of the pie (experiment 1). When the procedure allows participants to change their previously reported emotion, receivers choose to inflate their reported level of anger prior to proposers' decision (experiment 2). Finally, this emotion gaming hypothesis generalizes to positive emotions as well. In a standard trust game, trustees inflate the level of happiness before trusters decide on passing vs. keeping a fixed amount of money to the trustees (experiment 3).