Dams disrupt downstream riverine ecological communities and commonly cause altered benthic macroinvertebrate communities. It has been hypothesised, though rarely definitively tested, that unregulated tributaries can provide colonist species, as well as subsequent flow, nutrients, sediment, and organic matter to damaged regulated systems, thereby contributing to the recovery of rivers downstream of impoundments. We assessed the influence of three different sized unregulated tributaries on macroinvertebrate communities in riffles of the regulated Gwydir River, NSW, on nine occasions over two years. Quantitative macroinvertebrate samples were collected from regulated sites upstream and downstream of each tributary confluence (six sites in total) and two sites without an intervening tributary. Three sites within each unregulated tributary were also surveyed. Macroinvertebrate samples were identified to genus. The overall similarity of macroinvertebrate community structure remained relatively unchanged between regulated upstream and downstream sites compared to faunal differences between locations without a tributary. Differences in community composition were not associated with the magnitude and variability of tributary flows between each sampling occasion. Regulated community composition was significantly different to tributary communities. Although these differences were small, the regulated river sites were characterised by flat worms (Cura sp.) and larval hydroptilids (Orthotrichia sp.). Overall, we found little evidence to show that tributaries have any significant influence on macroinvertebrate community composition within the regulated river. Thus, the hypothesised recovery downstream of tributaries in regulated rivers was not supported. It is possible that regulated irrigation flows over summer (three months of bankfull flows) may homogenise macroinvertebrate communities and override any tributary influences. Additionally, tributary flows here have an overall small contribution to regulated flows, and the tributaries studied may be impaired by agricultural land use, which could detract from the ameliorating potential of an unregulated tributary.