<p>Aquatic macrophytes typically support greater macroinvertebrate abundance than bare riverbeds, largely due to habitat complexity. However, little is known about how macroinvertebrates are distributed within submerged macrophyte patches in lotic systems. We hypothesized that the middle parts of patches would support higher macroinvertebrate densities due to favorable refuge and feeding conditions. We sampled epiphytic macroinvertebrates at five intra-patch positions across 10 patches of the endangered submerged macrophyte <i>Ranunculus nipponicus</i> var. <i>submersus</i> in a spring-fed river in Japan. Unexpectedly, we found a previously unreported concentrated distribution of macroinvertebrates in the upstream parts of the patches. These parts showed approximately ninefold higher total mean density and twofold higher taxonomic richness than the downstream floating parts. The distributional pattern was consistent across functional feeding groups and habit traits, with 10 of 15 taxa reaching their maximum densities in the upstream parts. The underlying mechanisms remain unclear, as only a single sampling event was conducted, and few environmental variables were measured. Nevertheless, flow directionality may generate habitat heterogeneity within patches, representing an additional dimension of habitat complexity. Overall, our findings highlight the importance of sampling across multiple intra-patch positions to accurately characterize epiphytic macroinvertebrate communities in lotic systems.</p>