Research finds evidence for bias in frontline workers’ decision‐making affecting citizens, but important questions remain about the underlying causal logics: Which mechanisms may explain disparity in decision‐making for different demographic categories of citizens? To what extent is frontline workers’ decision‐making influenced by cognitive biases toward citizens similar to themselves (similarity bias) and by stereotypes? Focusing on gender bias and drawing on social identity theory and gender stereotype theory, this article examines how caseworker‐citizen gender similarity and gender stereotypes shape caseworkers’ decision‐making. Using (a) an experimental vignette, (b) measurement of gender stereotype beliefs from a Brief Implicit Association Test, and (c) quasi‐experimental administrative data, we examine the effects of gender similarity and gender stereotypes in the policy area of child visitation in Denmark. We find support for both gender similarity and gender stereotype expectations. Moreover, the effect of gender stereotypes appears slightly larger than that of gender similarity