The conservation of selectively logged tropical forests has received increasing attention, especially under the REDD+ scheme of the United Nations Framework Convention on Climate Change. However, knowledge of the structure of large-scale logged forests remains limited, especially in seasonally dry tropical regions, while there have been many studies on intact old-growth closed-canopy tropical forests. In this study, data from 327 plots were used in a large-scale forest inventory with systematic sampling covering 139,360 ha to reveal the condition of selectively logged mixed-deciduous forest managed traditionally under the Myanmar selection system (MSS). The overall averages (±SE) for the trees > 10 cm DBH were 140 ± 4.95 trees/ha for tree density, 6.18 ± 0.26 m²/ha for basal area and 66.2 ± 3.17 Mg/ha for aboveground biomass. These values are lower than or close to the lower end of the reported values in undisturbed or even disturbed tropical forests. There were very few harvestable large trees of commercial species. We conclude that there has been widespread large-scale forest degradation in the traditionally logged forest of our study site. The possible reasons for forest degradation include the shorter cutting-cycle than the MSS-standard of 30 years, more illegal logging for timber than legal logging, and local demand for charcoal. Restoration of the degraded forests should be prioritized, together with control of illegal logging.