Remnants of old forests left on the landscape following forest harvesting, especially corridors, provide benefits of connectivity and facilitation of movement or dispersal, which may be hindered by the presence of edges. Our objective was to determine the extent of edge influence on forest structure in these forest remnants in black spruce boreal forest. We sampled canopy cover and the density of trees, snags, and logs along clearcut edge–forest gradients in large forest patches, cutblock separators, and riparian buffers. The distance-of-edge influence was determined by comparing values at different distances from the edge to values in interior forest using randomization tests. Forest remnants had lower live tree density and canopy cover and higher mortality and windthrow than interior forest. Distance-of-edge influence on forest structure extended 10–30 m from the edge, and was slightly more extensive into cutblock separators where two edges are in close proximity, but was less extensive in riparian buffers, possibly due to the presence of stable internal edges near the stream. Because of edge influence, structure near the edges of forest remnants and across narrow corridors is modified; wider corridors would be required to provide a core habitat of interior forest conditions.