Background: In captivity, capuchin monkeys compete for space and rank. Fights can result in traumas, especially to the limbs, requiring interventions that are often outpatient. Local anesthesia as a tool in these procedures, as an aid to chemical restraint, is very relevant for small outpatient surgeries, or even for pain relief. Knowledge of peripheral nerve anatomy is essential to perform local anesthesia. Thus the objective of the present study was to determine, by anatomical studies of the brachial plexus region, the best access pathways for anesthetic blocking of the nerve.Materials, Methods & Results: Seven adult capuchin monkeys (Sapajus libidinosus) were used, weighing 2-3 kg, fixed and preserved in formaldehyde aqueous solution at 10%. In five of these animals the supraclavicular, infraclavicular and axillar regions were dissected to visualize the muscles, clavicle and bracchial plexus nerves. An analogical pachymeter was used to measure the depth of the plexus in relation to the cranial and caudal clavicle face and axillary fossa, comparing the length of two hypodermic needles (13x4.5 mm and 15x5 mm). Simulation of the anesthetic block was tested in two animals: before dissecting an acrylic varnish solution was injected using a syringe and 13x4.5 mm needle in the supraclavicular, infraclavicular regions and axillary fossa. To assess the positioning points of the syringe, dissection was performed and the varnish perfusion in the plexus was observed. For the anesthetic block in the supraclavicular region the dorsal median of the clavicle with a 95º deltoclavicular angle with the needle perpendicular to the skin was taken as point of reference. In the infraclavicular the reference point was the caudal face of the median clavicle with an 80º deltoclavicular angle. In the axillar region, with the limb at 90º, the syringe was positioned perpendicular to the axillar at the height of the mid portion of the thorax. The mean and standard deviation of the skin-brachial plexus distance for the supraclavicular, infraclavicular and axillar techniques were, respectively, 1.76 ± 0.1387 cm, 1.12 ± 0.239 cm and 1.59 ± 0.365 cm. These data showed the viability of executing the anesthesia technique by three access pathways. However, in the supraclavicular access pathway in the anesthetic simulation with the 13x4.5 mm hypodermic needle, the stain diffused to the plexus, showing, when compared with the 1.76 cm mean skin- plexus distance a safe distance to prevent the needle from perforating the nerve.Discussion: The techniques reported in the human literature for brachial plexus block presented a series of complications, with incomplete blocks and hemorrhages when the axillar access pathway was used and presented risk of pneumothorax in the supraclavicular. In the capuchin monkey the supraclavicular access pathway in anesthetic simulation with 13x4.5mm hypodermic needle showed a safe distance for the needle not to perforate the nerve, so that the use of this needle could be indicated in 2-3 kg animals. However, hypodermic needles are not recommended for use in this area because of the risk of perforating the subclavicular artery close to the plexus. As an alternative some anesthesiologists use the infraclavicular access pathway with atraumatic needles recommended for brachial plexus block, with relative success and fewer complications. Although the supraclavicular region showed the best depth in relation to the technique used here, anesthetic tests should be made to confirm the efficaciousness of executing the brachial plexus anesthetic technique in capuchin monkeys using atraumatic needles for nerve block.