Interpersonal threats to public identity consist of situations where another person intentionally attempts to illegitimately undermine one’s ability to display a valued and distinctive public identity. In three studies, we examined victims’ reactions to copycatting as an interpersonal threat to public identity to test each component of this definition. In Study, participants expressed the greatest degree of anger when the copying was illegitimate and intentional. In Study 2, participants expressed a greater degree of anger to copying of an important (vs. unimportant) characteristic. In Study 3, we manipulated the number of identity characteristics copied. A structural model showed that as the number of copied characteristics increased, participants’ perception of the situation as illegitimate and the copying as intentional predicted a threat to one’s freedom, which in turn predicted felt reactance predicting an unfavorable impression and a desire to confront the copycat. Together, the results support the definition of interpersonal threats to public identity and copycatting as such a situation.