Tropical Montane Cloud Forests (TMCF) support exceptional concentrations of biodiversity but are severely threatened by deforestation. In Mexico, 60% of TMCF tree species have been reported as threatened and the epiphytic plants characteristic of these forests are particularly vulnerable to disturbance and climate change. We evaluated the role of remnant TMCF fragments as reservoirs of tree and epiphytic bromeliad biodiversity in southeastern Mexico. In four cloud forest fragments of varying size (1.2, 4.1, 6.6 and 9.8 ha), we recorded all trees > 10 cm dbh in six 20 x 10 m plots and sampled eight trees at each site to measure bromeliad diversity. The assessment revealed that even very small forest fragments can host significant tree and epiphytic bromeliad diversity. In total, 45 tree and 18 bromeliad species were recorded across all the sites. These forest fragments are an important reservoir of endemic tree species (seven species) and of those with conservation status (nine tree species and one bromeliad species). Important variation was found among fragments in terms of tree and bromeliad composition. This high heterogeneity among forest sites means that maintenance of even small fragments can play a strategic role in the conservation of biodiversity in the severely transformed landscape of the region and is a strategy that merits full consideration in the design of forest management policies and TMCF restoration initiatives.