Monitoring ungulate populations is an essential part of wildlife management with ungulates performing essential ecosystem roles including structuring populations of large carnivores. A number of ungulate species in Southeast Asia are also globally threatened and are therefore important conservation targets in their own right. We estimated large (> 15 kg) ungulate densities in two protected areas, i.e. Mondulkiri Protected Forest and Phnom Prich Wildlife Sanctuary, in eastern Cambodia using distance-based line transect sampling. During the 2009/2010 and 2010/2011 dry seasons, we surveyed 110 line transects (randomly distributed across 3,406 km²) for a total of 1,310 km. We used DISTANCE 6.0 to model detection functions from observations of banteng Bos javanicus, wild pig Sus scrofa and red muntjac Muntiacus muntjak generating estimates of group density, cluster size and individual density. Estimated densities ± SE were 1.1 ± 0.2 individual banteng/km², 1.4 ± 0.4 individual wild pig/km² and 2.2 ± 0.2 individual red muntjac/km² giving an overall density of approximately 4.7 large ungulates/km². Although wild pig and red muntjac densities were within the range of estimates reported from ecologically similar protected areas in tropical Asia, overall large ungulate density is much lower than the intrinsic carrying capacity of deciduous dipterocarp forest. This appears largely to be due to the scarcity of large deer (i.e. hog deer Axis porcinus, sambur Cervus unicolor and Eld's deer Cervus eldii) as a result of extensive historic hunting. Current large ungulate densities appear too low to support a viable tiger Panthera tigris population in the long term, and ungulate recovery, driven by strong protected area management, needs to be achieved before tiger populations can be restored.