In everyday life, we communicate not only alone with another person but in front of others as well. Present study examined the effect of personal relationships between observer and dyad on facial behaviors during emotional communication. Pairs of friends viewed film clips that elicited positive affect and had a conversation in one of three conditions (a) observer absent, (b) stranger–observer, or (c) friend–observer. I video-recorded facial behavior of each participants and coded duration of smile, gaze and utterance. Participants filled out the questionnaire of emotion, public self-consciousness, internal other-consciousness, and satisfaction with conversation. Results showed that duration of utterance was longer in the friend–observer condition than the stranger–observer condition, but smiles and gazes did not differ among conditions. Observing by a friend seemed to facilitate emotional expressions on the intentional behavioral channel. Results of correlations between expressive behaviors and subjective indices suggest that friends made strategic use of nonverbal behavior in front of a stranger.