Individuals with high social anxiety (HSA) may experience subtle impairments in social processes that, if identified and targeted in treatment, could enhance social relationship functioning. Discordance in positive affect (PA), i.e., mismatch between PA experience and expression, may be one impactful treatment target if it is prevalent among HSA and if it weakens social bonds. The current study tested whether, during a positive social interaction: 1) a cross-section of individuals with HSA vs. low social anxiety display heterogeneous, highly distinct “PA profiles,” reflecting four patterns of discordant or concordant PA; 2) displaying discordant profiles is linked to HSA, and displaying all predicted profiles aside from concordant high PA is linked to additional clinical symptoms; 3) discordance is associated with lower desire for future interaction (DFI) with one’s conversation partner and with conversation partners’ lower reciprocal DFI; and 4) discordant profiles reflect use of specific emotion regulation strategies. Ninety-six adults age 18-55 participated, with scores on the Liebowitz Social Anxiety Scale either ≥ 50 (HSA; n = 70) or ≤ 20 (n = 26). All engaged in a positive laboratory-based relationship formation task with a confederate conversation partner and rated their internally felt PA several times during the interaction. Next, participants and confederates rated their DFI, and participants rated their use of emotion regulation strategies. Automated software was later used to code video recordings of participants’ intensity of smiling. Latent profile analysis tested for the predicted PA profiles. Three of the four predicted profiles emerged, including one concordant high (n = 21), one concordant low (n = 23), and one discordant (high felt, low expressed) PA profile (n = 52). Compared to either of the other two profiles, displaying concordant low PA was associated with higher social anxiety, higher anhedonic depression, and higher use of expressive suppression to regulate emotions. Discordant PA was not more strongly associated with HSA and was not maladaptive for DFI. Instead, concordant low internally felt and low expressed PA was identified as a potentially useful indicator of both clinical severity and impairment in social relationship functioning and may point to more urgent or intensive treatment need.