There are individual differences in how people respond to emotionally ambiguous cues (i.e., valence bias), which have important consequences for mental health, development, and social functioning, yet how these differences develop in childhood and adolescence is unknown. Extensive literature shows that children's cognitive biases, including appraisals in uncertain situations, can be influenced by parents. The current study collected valence bias from parent and child dyads (n = 136, children ages 6-17 years, M = 10.92, SD = 3.22) using a dual-valence ambiguity task (i.e., the valence bias task). Using structural equation modeling, we found that a child's valence bias was associated with their parent's valence bias ([beta] = 0.283, p = 0.005). We also explored the effect of parent-child attachment in three facets (communication, alienation, and trust) on this intergenerational transmission. Communication moderated the relationship between parent and child valence bias, such that higher communication led to a stronger relationship between parent and child valence bias ([beta] = 0.03, p = 0.04). These findings suggest that one mechanism that supports valence bias development is the parent's bias, and this may be uniquely influenced by the degree of parent-child communication. This tendency to similarly interpret ambiguous stimuli may result from social learning. Specifically, our results support a theory of generalized shared reality where parents and children who have a greater interpersonal connection (i.e., communication) also share a more similar world view (i.e., valence bias). A video abstract of this article can be viewed at https://www.youtube.com/watch?v=xlSDxFDmP7g