Negatively biased facial affect discernment may prompt socially inhibited behavior. Characterizing normative patterns of facial affect discernment across emotions and expression intensity during middle childhood will help to identify subtle, yet meaningful, deviations that may emerge for individuals and potentially negatively impact their social behavior. Facial affect discernment for happy, sad, and angry expressions across low, medium, and high intensities and parent-reported socially inhibited behavior were measured in this study in a sample of 7-10 year-old children (N = 80; 53% female). Discernment accuracy improved with increased expression intensity for all emotions. Specifically, we found a quartic effect for the association between intensity and accuracy for anger and negative quadratics effects with decelerating positive rates of changes for associations between intensity and accuracy for happiness and intensity and accuracy for sadness. Additionally, discernment accuracy for happiness was generally better than for sadness and anger; discernment accuracy for anger was generally better than for sadness. However, at low intensity, discernment accuracy for sadness was comparable to accuracy for happiness but better than for anger. Neither misidentification of neutral and low intensity faces as negative nor discernment accuracy of happiness at low intensity was significantly associated with socially inhibited behaviors. Although accurate discernment of anger and sadness at low intensity was not significantly related to socially inhibited behavior, better discernment accuracy of anger and sadness at medium intensity was significantly related to more socially inhibited behavior. Overall, these results enhance understanding of normative facial affect discernment and its relation to maladaptive social behaviors in middle childhood, a developmental stage at which intervention efforts may prove effective at heading off detrimental outcomes associated with socially inhibited behavior such as loneliness, low self-esteem, peer victimization, social anxiety, and depression that increase in late childhood and adolescence.