Mathematical and spatial reasoning abilities during childhood predict later success in male-dominated science, technology, engineering, and math (STEM) disciplines, yet relatively little is known about the affective correlates of children's math and spatial performance or gender differences therein. In the present research, we assessed math and spatial anxiety in 394 elementary schoolchildren (ages 6 to 12 years) and investigated their relations to math achievement and spatial reasoning performance, respectively. In addition, we evaluated children's verbal anxiety and reading ability to determine the domain specificity of relations between anxiety and cognitive performance during childhood. At the zero-order level, math, spatial, and verbal anxiety were moderately correlated with one another and with children's performance in the corresponding cognitive domains. Importantly, however, all three forms of anxiety displayed some domain specificity in their relations to cognitive performance. Gender differences in math and spatial anxiety were also domain-specific, with girls reporting significantly greater math and spatial anxiety, but not verbal anxiety, across the age range tested. These results demonstrate that math and spatial anxiety represent unique constructs early in development, exhibiting specificity in their associations with gender and cognitive performance during the first years of formal schooling. [This is the online version of an article published in "Developmental Psychology" (ISSN 0012-1649). For the final published version of this article, see?EJ1194987.]