An 18-month-old, neutered female West Highland White Terrier was presented for urinary incontinence during sleep. Urinary incontinence was observed 8 months after neutering. There were no significant findings on clinical examinations. Because hormone-responsive urinary incontinence was diagnosed presumptively based on the information provided by the owner, oral oestradiol therapy was started. As a result of the measurement of serum oestradiol concentration at the initial presentation, the level of serum oestradiol was lower than found in healthy dogs. After oestradiol was orally administered a total of three times, the dog has been asymptomatic for more than two years. Mild dermatitis appeared temporarily as a side effect. At 753 days after the initial presentation, the dog was generally in good condition without any sign of recurrence. The result of this case suggested that oral oestradiol therapy for hormone-responsive urinary incontinence could replace conventional medical therapy in terms of treatment effect, reduction of frequency of administration and side effects.