On 4 January 1965 the submarine got underway for her second Mediterranean deployment, stopping at Lisbon, Portugal; and Rota, Spain; before beginning a series of exercises with North Atlantic Treaty Organization (NATO) forces off Italy and Turkey. The boat sailed for home from Athens, Greece, on 14 April and arrived, via Rota, on 2 May. "Chivo" spent the rest of the year conducting her usual local training operations, including a specialized mine planting exercise. A regularly scheduled five-month overhaul took place at Charleston in early 1966, followed by type training and the usual ASW services to various Atlantic Fleet units. During this period "Chivo" also participated in the final weapons range acceptance tests for the Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahama Islands.