"Haverfield" returned to Pearl Harbor March 1965 and, after joining Escort Squadron 5, sailed on 19 June 1965 for duty off of South Vietnam. There she participated in Operation Market Time patrols to guard against the infiltration of North Vietnamese troops and supplies to Viet Cong irregulars in South Vietnam by sea. She served on "Market Time" station for seven months, then returned to Pearl Harbor on 2 February 1966. Departing for the Far East 23 May, she resumed "Market Time" operations on 9 June. Eleven days later, she participated in the most significant action of the operation up to that time.