Macroinvertebrate drift is a process in which invertebrates are transported from tributaries to the mainstem river, serving as a direct food resource for fish and playing a crucial role in the river’s food web by transferring nutrients between habitats. The Kootenai River is a large transboundary river that flows from Canada through Montana and Idaho before re-entering Canada and contributing to the Columbia River. The oligotrophic river relies on its tributaries to supply resources, including macroinvertebrates, to sustain the mainstem ecosystem. To begin to assess the role of tributaries in sustaining the Kootenai River food web resources, we examined the abundance and diversity of macroinvertebrate drift from three tributaries of the Kootenai River during two consecutive summers. We sampled every four hours throughout a 24 hour period to examine fluctuations in resource availability. Collected macroinvertebrates are being identified to the genus level, when possible. Preliminary results indicate an average of 1038 individuals per four hour sampling period. The average taxa richness is 34 genera with evenness of approximately 0.8. This research highlights the critical role of macroinvertebrates from tributaries in supporting the ecosystem and informs conservation measures for the Kootenai River’s vulnerable fish populations.