Plant litter decomposition varies by species and environmental conditions. To study environmental controls of decomposition, we measured plant litter decomposition rates in six wetlands located in West Virginia, USA. Four common wetland litter species were used: broadleaf cattail (Typha latifolia L.), common rush (Juncus effusus L.), brookside alder (Alnus serrulata (Ait.) Willd.), and reed canary grass (Phalaris arundinacea L.). A fifth litter type was created from a mix of common rush, brookside alder, and reed canary grass. Litter bags were collected over two years, from December 2007 to December 2009, and environmental variables near litter bags were measured every two weeks. Nine environmental parameters and one study parameter were then used to construct and test the ability of 22 a-priori models to predict the decomposition rate of each litter type. The environmental variables that most influenced and, therefore, best predicted decomposition rate varied among litter types. Brookside alder decomposition rate was best predicted by soil temperature (ST), water pH (WPH), and the number of transitions between flooded and exposed conditions (FET); reed canary grass decomposition rate was best predicted by air temperature (AT), WPH, and ST; common rush decomposition rates were best predicted by AT; broadleaf cattail decomposition rate was best predicted by hydroperiod (HP) and FET; and the mixed litter decomposition rate was best predicted by AT and WPH. Overall, AT, ST, and WPH were directly related to decomposition rate, while HP was inversely related. The FET was directly related to decomposition rates of common rush and broadleaf cattail and inversely related to the decomposition rate of brookside alder. The study of litter decomposition helps reveal the link between environmental conditions and wetland function.