Callirhytis cornigera (Osten Sacken) is a gall wasp that has alternating agamic and sexual generations that develop in large, woody stem galls and small, blister-like leaf galls, respectively, on pin oak, Quercus palustris Muenchhausen. We assessed the spatial distribution of the leaf galls within leaves, shoots, canopy levels, and whole trees, and examined the relationship between leaf gall density and various tree parameters. Within leaves, proportionately more galls were located on primary lateral veins (59.5%) or midveins (38.1%), as compared with the petioles (2.0%) or secondary lateral veins (0.4%). As many as 18 galls occurred on individual leaves, but most leaves contained 0–4 galls. Some current-year shoots contained as many as 132 leaf galls, but most shoots had <20 galls. Leaf gall density did not vary significantly among heights within individual tree canopies, but was highly variable between trees. Leaf gall density at the whole tree level was not related to the tree’s rate of leaf- or shoot expansion. There was no relationship between tree-wide density of leaf galls and overall levels of foliar nitrogen, nonstructural carbohydrates, or protein binding capacity. The leaf galls supported a complex of hymenopteran parasitoids, including Aprostocetus spp., Pentastichus spp. (Eulophidae), Sycophila spp., Eurytoma sp. (Eurytomidae), Brasema sp. (Eupelmidae), and Ormyrus labotus Walker (Ormyridae). Parasitoids and inquilines accounted for nearly 80% mortality of C. cornigera within leaf galls; however, parasitism was only weakly density-dependent, regardless of spatial scale. Implications of these findings for management of C. cornigera are discussed.