A 1-year-old golden comet hen (Gallus gallus forma domestica) was presented because of an enlarged abdomen, cessation in egg production, difficulty in ambulating, and difficulty roosting. Results of radiographs and ultrasound examination revealed a radiolucent oval area in the right coelom and fluid with flocculent debris throughout the coelomic cavity. Escherichia coli and Proteus species were cultured from a sample of the fluid. Antibiotic therapy was temporarily beneficial, but the problem persisted and the hen was euthanatized. At necropsy, the oviduct was impacted with yellow caseous material. The diagnosis was colibacillosis and egg yolk peritonitis, which may have originated from an impacted oviduct.