The way children express and respond to emotions when they first meet is crucial to friendship initiation. But for highly shy children, these exchanges are particularly challenging. Existing research is based on individual and total frequency measures of emotion that do not reflect the transactional and dynamic nature of emotions in real-life peer interactions. We examined how shyness and dyadic similarity in shyness influence children's moment-to-moment dyadic emotion sequences with a new peer. Thirty age- and gender-matched dyads (Mage = 10.13 years, 75.8% White) were observed during an unstructured "getting to know you" task. Children's shyness was assessed through parent- and child-report. Using grid-sequence analysis (Brinberg et al., 2017) we identified three dyadic emotion clusters: Flexible and Shared Positive Affect (60%), Flexible and Shared Neutral Affect (35%), and Stable and Shared Negative Affect (17%). Children in the Stable and Shared Negative Affect cluster were rated higher in shyness relative to children in the Flexible and Shared Positive Affect cluster. Further, children more similar in shyness to their dyadic partner displayed more stable negative and neutral affect expressions than children who differed in shyness from their partner. Together, these findings suggest that shyness is related to less positive and less flexible emotion expressions when meeting a new peer, holding critical implications for friendship initiation among children varying in shyness. (PsycInfo Database Record (c) 2023 APA, all rights reserved).