A 10 yr old spayed female toy poodle was presented to a tertiary referral center for a 10 day history of waxing and waning lethargy, vomiting, diarrhea, and anorexia. An immune-mediated neutropenia (IMN) was suspected to be the underlying cause of her clinical signs. A bone marrow aspirate was obtained from the chostochondral junction of the 11th and 12th ribs on the right side and provided a definitive diagnosis of IMN. A positive response to therapy and repeat blood work further confirmed the diagnosis. Obtaining bone marrow aspirates from the chostochondral junction is a safe, cheap, and reliable method of diagnosing IMN and can be performed in the private practice setting with light sedation and minimal need for specialized equipment.