Dam removal is increasingly employed as a river restoration tool.  However, over time, rivers adjust to the presence of dams and dam removal represents a change in the hydrologic regime.  Since sediment-filled dams typically cause minor alterations to flow or temperature, the ecological impacts associated with their removal may primarily be associated with sediment released from the decommissioned reservoir.  Prior to and following the removal of a small sediment-filled dam from a montane river in western Oregon, we examined channel morphology, water quality, and benthic macroinvertebrate density, taxa richness, and community composition over time.  Dam removal itself and subsequent sediment transport episodes were transient and appeared to have no effect on downstream macroinvertebrate populations.  However, when a single rain storm event eroded 1134 m³ of sediment (86% of total reservoir erosion) in less than 2 days, macroinvertebrate density and taxa richness declined significantly downstream of the dam site, compared to upstream.  Macroinvertebrate density recovered relatively quickly, but community similarity and taxa richness remained reduced.  Changes in macroinvertebrate community composition were largely associated with the loss of rare species and increase of sediment-tolerant oligochaetes, possibly due to changes in geomorphic conditions downstream of the former dam.