Streptomyces spp. are common symbionts of the leaf-cutting ant species Acromyrmex octospinosus, which feeds on basidiomycete fungus leaf matter and harvests the lipid- and carbohydrate-rich gongylidia as a food source. A. octospinosus and other ant genera use antifungal compounds produced by Streptomyces spp. and other actinomycetes in order to help defend their fungal gardens from parasitic fungi. Herein, we report the draft genome sequence of Streptomyces strain S4, an antifungal-producing symbiont of A. octospinosus.