OBJECTIVES: To describe the ultrasound-guided transversus abdominis plane (TAP) block using a subcostal oblique approach in dog cadavers and to evaluate the spread of a methylene blue solution using a multiple-injection technique. STUDY DESIGN: Prospective, descriptive, experimental anatomic study. ANIMALS: Nine adult Beagle cadavers weighing a mean ± standard deviation of 13 ± 2 kg. METHODS: Methylene blue solution (10.0 mL) was injected bilaterally within the fascia that overlies the transversus abdominis muscle in dog cadavers under ultrasound guidance. A total of three injections (3.3 mL each) were administered on each side by the same operator. Dissection was performed by a second operator 20 minutes later. Successful nerve staining was defined as the presence of dye on the nerve for a length of >1 cm. RESULTS: Ventral branches of the T9, T10, T11, T12 and T13 nerves innervating the cranial abdominal wall were stained in 72%, 95%, 100%, 95% and 61% of cases, respectively. Ventral branches of L1 and L2 innervating the caudal abdominal wall were stained in only 33% and 11% of cases, respectively. The dye was found only in the fascia between the transversus abdominis and the internal oblique muscles. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrasound-guided subcostal oblique TAP block provided adequate staining of the sensory innervation of the cranial abdominal wall. Further studies are required to evaluate the efficacy of this technique in blocking the nociceptive response in clinical procedures.