Welch was laid down on 8 May 1967 by Peterson Builders, at Sturgeon Bay, Wis.; launched on 25 July 1968; sponsored by Mrs. Roy G. Anderson; and commissioned at the Boston Naval Shipyard on 8 September 1969, Lt. Paul F. Woods in command.

Welch completed her first Vietnam tour on 31 January 1971 and, after stops at Hong Kong and Subic Bay, reentered Apra Harbor on 20 February 1971.

On the 20th, she relieved USS Gallup at Camranh Bay, South Vietnam, and resumed Market Time patrols with TF 115.

Welch's voyage back to her base took her to Singapore, to Zamboanga and Subic Bay in the Philippines, and to Koror in the Palau Islands, before she arrived in Guam on 10 January 1972.

After almost two months of operations in the Philippines, the gunboat departed Subic Bay on 16 June and arrived off the coast of South Vietnam three days later.

Instead of Market Time patrols, Welch spent the first 25 days on station in the Gulf of Tonkin, testing the gunboat's capabilities for sustained operations at sea.

Her ensuing three months of service laboring to stop the flow of communist supplies were broken but once when she departed Vietnamese waters for a three-day visit to Bangkok.

In the following month, Welch conducted a surveillance patrol in the northern Marianas between 11 and 18 December and then ended the year in port at Apra Harbor.

Early in February 1973, the warship deployed to the Philippines where she spent the middle of the month engaged in high-speed missile boat attack exercises with larger ships of the Pacific Fleet.

In order to be available upon arrival of the parts needed to repair her gas turbine, Welch remained in the immediate vicinity of Guam until the end of October, but for three brief interruptions.

On 24 May, she put to sea to rescue Yukiko Maru and towed the disabled Japanese ship into Apra Harbor the following day.

En route to Subic Bay, the three ships participated in a high-speed missile boat attack exercise with USS Midway and her escorts.

On 18 February, Welch entered Subic Bay and, while there, put to sea briefly for another missile boat exercise, this time with the USS Oriskany task group.