Chrosomus cumberlandensis (Blackside Dace) is a federally protected cyprinid fish found in small tributaries of the upper Cumberland River system in southeastern Kentucky and northeastern Tennessee. Relatively little is known about the species’ reproductive ecology and early life history. From a small number of field observations, the species is known to spawn as an associate with other cyprinid nest-building hosts, namely Campostoma anomalum (Central Stoneroller) and Semotilus atromaculatus (Creek Chub). In the present study, we first analyzed Blackside Dace co-occurrence patterns with other cyprinids to predict the relative importance of each species to Blackside Dace nestassociation behavior. We next studied Blackside Dace spawning activities in seven 200-m reaches in five Kentucky streams during May-July 2006 to document nest associations and measure microhabitat conditions at spawning and non-spawning locations. Three of the seven study reaches were impacted by active logging operations. We observed 25 Blackside Dace spawning events, and all 25 were associated with Creek Chub nests, consistent with predictions from our species co-occurrence analysis. Spawning microhabitats were located in areas with significantly greater mean wetted-channel widths, slower column and bottom velocities, lower silt levels, lower substrate embeddedness, and larger subdominant substrate particles compared to non-spawning microhabitats. Study reaches with adjacent active logging had significantly greater mean silt levels, substrate embeddedness, water temperature, and conductivity values compared to reaches with no active logging, although 4 of the 25 spawning events occurred in reaches with active logging. Our results highlight the importance of cyprinid nest-building hosts (especially Creek Chub) to Blackside Dace reproductive ecology, and they also reinforce the need to maintain the integrity of Blackside Dace streams at the whole-community level.