Growing demand for non-timber forest ecosystem services has resulted in increased use of partial harvesting in boreal forests. Since the 1990s, multiple studies have yielded short-term responses to partial harvesting. Here we present an inventory of longer-term (20 years) responses of overstory and understory trees to partial harvesting in aspen-dominated boreal mixedwood stands. Pre- and post-harvesting overstory trees were mapped and measured for total height and diameter at breast height (DBH); understory trees were measured for total height. Codes identify tree species, treatments, and years since harvest. Data are stored in separate Microsoft Excel spreadsheets: overstory trees, understory trees, and years after harvesting.