Rangeland degradation compromises the functioning of extensive natural ecosystems and threatens pastoral livelihoods worldwide. Yet, defining rangeland degradation and its underlying causes remains controversial. In this study we review rangeland studies to identify different approaches used to assess rangeland degradation in Mongolia, where the prevalence of degradation is frequently referenced in media and policy documents. We compiled studies addressing rangeland degradation, with a special emphasis on the grey literature, to assess: 1) how different studies defined and quantified rangeland degradation; 2) whether a theoretical background was explicitly mentioned; 3) which drivers of degradation were identified and whether their effects were quantified; and 4) the distribution of the studies across relevant environmental gradients. We found 114 studies published between 1950 and 2021. Degradation was frequently assessed as a change in vegetation or land cover, but there was no standard definition of rangeland degradation and only a few studies explicitly defined contrasting degradation levels (19 studies). Less than one third of studies (27) referred to a theoretical framework. Grazing and climate (precipitation and temperature), alone or in combination, were most frequently mentioned as drivers of degradation but the impact of different drivers differed across ecological zones. The majority of studies were conducted in the steppe, forest steppe and desert steppe zones of central Mongolia. Future studies should consider the differences in ecological potential of each rangeland and quantify the relative importance of different drivers in each ecological zone. Emerging initiatives for rangeland assessment and monitoring that use long-term data collection following standardized methodologies based on robust theoretical frameworks hold promise for the design of policies and strategies for sustainable land use in Mongolia.