SummaryDecomposition of plant litter is a key process in the flow of energy and nutrients in ecosystems. The extent and mechanisms towards which climate warming will affect litter decomposition in plateau wetlands remains largely unknown.We conducted a two‐year litter decomposition experiment along an elevation gradient from 1891 to 3260 m in China using litter from two dominant species of plateau wetland plants to determine the influences of temperature, litter quality and litter mixing on decomposition.The decomposition rate was significantly correlated with water temperature during the plant growing seasons and with litter quality during the winters. The temperature sensitivity of litter decomposition (Q10) wasc. 3.02 along the elevation gradient, but mixed litter was more sensitive to temperature than the litter of eitherScirpus tabernaemontani(grey club‐rush: Cyperaceae) orZizania caduciflora(wild rice: Gramineae) alone.The concentration of nitrogen (N) and the ratio of N:P (phosphorus) had positive effects but the concentration of carbon (C) and the ratios of C:N and lignin:N had negative effects on the decomposition rate, especially during the winter. In addition, N concentration and the ratio of C:N were more significantly correlated with decomposition rate during the first winter, while the ratio of lignin:N was more significantly correlated with decomposition during the second winter.Consequently, climate warming may significantly impact biogeochemical cycling of plateau wetlands, notably C storage.