Many field-collected fungal specimens are maintained in herbaria worldwide. These specimens contain an untapped wealth of taxonomic and ecological fungal biodiversity information. However, DNA can be difficult to obtain from preserved specimens. We present a DNA barcoding protocol specifically for preserved fungal specimens (ascomycetes and basidiomycetes). The E.C. Smith Herbarium at Acadia University houses 20,000 fungal specimens representative of northeastern North America. We achieved a DNA barcoding success rate of 18% from pre-1980 specimens (n = 39) using a kit-based DNA extraction protocol and sequencing of the full internal transcribed spacer (ITS) region of ribosomal DNA. This result surpassed success rates of previous protocols. We also explored the use of mini-barcodes from the ITS1 region only. Mini-barcodes (n = 13) demonstrated a 92% success rate in post-1980 specimens compared to full barcodes (46% success rate, n = 13) while retaining all the identification power of full barcodes in the examined specimens. Our approach will enable herbarium collections to be used more efficiently to populate DNA sequence databases such as GenBank. This approach will expand the number of reference DNA barcode sequences from vouchered fungal specimens within publicly available databases.