Six Armillaria species were found in western Oregon and Washington: A. solidipes, A. sinapina, A. gallica, A. nabsnona, A. cepistipes, and A. altimontana. Of these, A. solidipes is known as an aggressive root disease pathogen that causes significant growth loss and mortality in conifers. Under certain environmental, host, and plant community conditions, A. solidipes was found in a non-pathogenic state. In this situation, A. solidipes can be difficult to distinguish from other Armillaria spp. on the basis of signs and symptoms. Ecological roles of A. gallica, A. sinapina, A. nabsnona, A. cepistipes, and A. altimontana have been generally characterized as primarily saprophytic to weakly pathogenic. However, recent observations suggest that these species can also be associated with deteriorating forest health, which frequently results in tree mortality. In particular, A. nabsnona and A. cepistipes both appear to be more common in the region than was previously known, and both were found in association with a combination of dead, dying, and/or apparently diseased hardwoods. In this study, we used DNA-based methods to confirm species identification and utilized location-specific climate data for bioclimatic modeling to predict where Armillaria spp. are likely to occur under changing climates. Models are presented for contemporary and future time periods.