The fate of vascular plant detritus and the microbial communities and processes involved during the decomposition of litter are important aspects in elucidating energy flow and nutrient cycling in wetlands. Therefore, we collected and identified conspicuous fungal sporocarps in situ and isolated microfungi from living and dead Typha latifolia (cattail) leaf tissues. Cattail is a dominant plant species in southern boreal and temperate marshes and abundant in the Low Boreal Mixedwood ecoregion in central Alberta, Canada. Following two successive field collections in early and late summer 2001, 45 different fungal taxa were identified. There were 26 ascomycetes, five basidiomycetes, and 14 anamorphic taxa, most of them with putative ascomycetous affinities. Twenty-four taxa represented new records for T. latifolia, 12 were new to Canada, and seven were new to North America. Also, five taxa were new reports outside of the country of the type locality. To elucidate their roles in the decomposition of T. latifolia leaves, we examined 33 taxa for their ability to use cellulose, gelatin, starch, tannic acid, and lignin as carbon sources (based on calorimetric tests), as well as to cause mass losses of sterile T. latifolia leaves. The number of fungi using cellulose and gelatin as carbon sources was significantly greater than those using starch, tannic acid, or lignin. Mass losses of T. latifolia leaf tissues by ascomycetes and basidiomycetes ranged from 1.3 to 54.6% and −0.4 to 52.1%, respectively. There was a positive relationship between mass loss of T. latifolia leaves and cellulose degradation but not between mass loss and any of the other carbon sources. Our data showed that a taxonomically diverse suite of fungi effectively degrades this plant material; however, additional studies examining the decomposer communities of other dominant wetland plants are necessary to gain a better understanding of nutrient and energy dynamics in wetlands at the ecosystem level.