This research deals with the interplay between language use and social identity. Social lexical markers used by two leaders of two opposed groups (French and American presidents) on the Second Gulf War were identified. Experimental texts were constructed on this basis and were read by French participants. The authors compared two types of social identity activation, either indirect (in-group vs. out-group lexical markers) or direct (in-group vs. neutral priming). Attitude and intergroup perception were measured on three groups (French, American, and Iraqi). Whereas no effect of direct activation was observed, results notably showed that using out-group marker leads participants to emphasize their in-group attitude, whereas an in-group marker leads them to "open-up" toward out-group attitude. Besides, an interesting in-group bias was evidenced despite the use of negatives outcomes and the three groups' evaluation. Potential applications for intergroup communication are discussed and theoretical and practical elaborations are proposed.