"Theodore E. Chandler"s next deployment coincided with the beginning of the United States's extensive buildup in Vietnam. On 19 June, she departed the west coast with ASW Group 1 bound for what appeared to be a normal peacetime deployment to the western Pacific. However, on 2 August, North Vietnamese torpedo boats allegedly made a torpedo attack upon the destroyer while she cruised international waters in the Gulf of Tonkin. "Theodore E. Chandler" received orders to join the ASW screen of carriers dispatched to deliver air strikes on North Vietnamese torpedo boat bases. After the strikes, the warship resumed her normal duties with ASW Group 1 and the 7th Fleet.