This study aimed to investigate how individuals form impressions about the self-esteem and life satisfaction of a male who engages in muscle talk on Facebook. The study examined (a) how a target's body build and peer-generated comments influence observers' impression of him, and (b) how such influences might be moderated by the cultural backgrounds of observers (Asian Americans and European Americans). A mock-up Facebook profile page was created in which two factors were manipulated: the target's body build (muscular, average, and overweight) and peer-generated messages (muscle encouraging and muscle discouraging), creating six different conditions. Male college students (N = 508) were randomly assigned to one of the conditions. After viewing a mock-up Facebook page online, participants completed an online questionnaire assessing their impressions of the target's self-esteem and life satisfaction. Results showed that a muscular target was perceived as possessing higher levels of self-esteem and life satisfaction. Observers rated the target as having higher self-esteem when the target received muscle-encouraging messages than when the target received muscle-discouraging messages. No cultural differences were identified. Findings suggest the existence of weight bias when forming psychological impressions of others online. Findings also confirmed the important role of peer-generated messages in the impression formation process online.