We determined the in vitro galactomannan reactivity of isolates recovered from 17 patients with invasive phaeohyphomycosis, 4 of whom had positive galactomannan antigenemia. All isolates were nonreactive using the galactomannan immunoassay. Galactomannan antigenemia in patients with phaeohyphomycosis should raise the possibility of concomitant invasive aspergillosis.