Previous research showed that children can exhibit preferences for social categories already at preschool age. One of the crucial factors in the development of children’s attitudes toward others is children’s observation and imitation of adults’ nonverbal messages. The aim of our study is to examine whether children’s tendency to perceive and follow nonverbally expressed attitudes toward other people is related to ingroup bias, i.e. the tendency to favor one’s own group over other groups. We examined 175 preschool children (age in months: 61–87; M = 72.6, SD = 6.53) presenting them with a video of a conversation between a message sender and a message recipient. The study was conducted in a minimal group paradigm. We found that children accurately identified the message sender’s attitude toward the recipient and also generalized this attitude to other members of the new group. We also found explicit ingroup bias among children from the message sender’s group. However, no generalization of the sender’s attitude to other ingroup members was found. The results are discussed in reference to previous findings on the role of imitation of adult’s non-verbal behavior for the development of social attitudes among children.