Allochthonous energy from leaf litter drives the carbon (C) budget of food webs in forested stream networks. Flow intermittency hinders these decay processes and alters macroinvertebrate community composition, a key mechanism of litter decay, through reduced habitat availability and detrital access. Intermittency naturally occurs in many headwater streams, but its global occurrence is increasing due to climatic and anthropogenic effects. Therefore, studying the interconnected biotic and abiotic impacts of flow intermittency in forested river networks is critical to understand C fluxes in these systems. To understand how intermittency alters macroinvertebrate community structure and litter decomposition, we deployed fine- and coarse-mesh litter packs across a network of 10 study reaches in the Gulf Coastal Plain region of central Alabama, U.S.A., during June–July 2023 and March–May 2024. We classified each stream as intermittently or perennially flowing based on qualitative observations and quantitative flow data from streamflow loggers. We quantified first-order decay coefficients (k, day-1) per reach, mesh treatment, and season, and identified all macroinvertebrates in each litter pack to genus or subfamily level. We hypothesized that: 1) ɑ diversity of macroinvertebrates will decrease with intermittency for the overall community and for shredders specifically, due to habitat loss and environmental filtering; 2) leaf litter decay will slow with intermittency, due to reduced biotic fragmentation. Across deployments, intermittency was not correlated with litter decay rate or macroinvertebrate ɑ diversity, though the coefficient of variation among decay rates was greater in intermittent reaches than in perennial reaches (p = 0.001). During the 2024 deployment, greater macroinvertebrate abundance led to faster litter decay, for macroinvertebrate communities overall (p = 0.001, R2 = 0.67) and shredders alone (p < 0.001, R2 = 0.74). Our results show that detrital resource processing is not exclusively flow-limited, but driven by the complex interplay between biotic and abiotic factors.