The ability to differentiate cardiac from noncardiac causes of respiratory distress is critical for enabling rapid initiation of appropriate treatment. FOCUS (focused cardiac ultrasound) is used in human medicine to help assess dyspneic patients in emergency situations. This study evaluated the use of FOCUS for differentiating cardiac from noncardiac causes of respiratory distress in veterinary patients. Emergency medicine and critical care clinicians categorized 38 dogs with respiratory distress as cardiac or noncardiac both before and after FOCUS. The accuracy of these diagnoses was calculated against a reference diagnosis, which was determined on the basis of consensus between a board-certified cardiologist and a board-certified emergency medicine and critical care specialist. Overall percent agreement between the emergency clinician and the reference diagnosis was 77.1% before FOCUS and 85.7% after FOCUS. Although FOCUS was helpful as compared with a physical examination and medical history alone, the difference was not statistically significant. In addition, a small percentage of dogs remained incorrectly diagnosed post-FOCUS. FOCUS also did not change the percent agreement between diagnoses made by faculty versus those made by residents.