Ten isolates of Verticillium biguttatum were obtained from sclerotia of Rhizoctonia solani on potato tubers in Erzurum, Turkey. The interaction between V. biguttatum and R. solani was studied in vitro and in vivo. V. biguttatum isolates affected R. solani by antibiosis and parasitism. All isolates of V. biguttatum inhibited the growth of R. solani colony. After the coiling around of R. solani hyphae, V. biguttatum hyphae penetrated host cell walls and grew within the hyphae. Viability of hyphae and sclerotia of R. solani was reduced by V. biguttatum isolates. V. biguttatum also significantly reduced the disease severity of R. solani on potato sprouts in pot experiments. This is the first report of V. biguttatum from sclerotia of R. solani in Turkey.