Little is known about how group bias may impact children's acceptance of unsubstantiated claims. Most children view cheating as unfair. However, in competitive situations, when ambiguity surrounds the potential intention to cheat, group affiliation may lead children to support claims of cheating based solely on the team affiliation of the claimant, even when those claims are not clearly substantiated. Therefore, it may be particularly important to consider the role ingroup bias may play in children's accusations of cheating in a competitive intergroup context. The current study investigated 4–10 year old children's (N = 137, MAge = 6.71 years, SDAge = 1.49; 47 % female) evaluations of ambiguous acts and unverified claims about those acts in a competitive, intergroup context. Results showed that children initially viewed an ambiguous act similarly, regardless of team affiliation, but demonstrated increasing ingroup biases after claims of wrongdoing were introduced. Implications for how unsubstantiated claims may impact intergroup interactions more broadly will be discussed.