After a refit, the Parche went to sea on June 17th, 1944 for her second war patrol which was again south of Formosa. Parche joined forces with submarines USS Hammerhead (SS-364) and USS Steelhead (SS-280), creating a coordinated attack group with Commander L. S. Parks, as the group Commander. A week later she sighted a patrol vessel and sounded "Battle Stations: Surface". Parche began firing with her deck guns and destroyed the trawlers deckhouse bringing down the antenna and after mast.

The patrol craft was maneuvering wildly at top speed until a round hit and jammed the rudder full left. With the patrol craft now running in circles to port, Parche would blow away the crafts deck gunners to kingdom come with gunfire on two attempts to man their weapons. A well placed shot in the stern crippled the craft and it was then set on fire with 20mm incendiaries. After burning intensely for ten minutes the vessel finally began to sink with six survivors scrambling out of the forward hold. One survivor attempted to thwart detection by putting a wooden cask over his head and peering out through the bunghole. That ruse, for him unfortunately, was not quite successful.

On the fourth of July, a three-ship formation was spotted shortly after midnight. The Parche gave chase until 0055 when, as Captain Ramage records it, "Our Fourth of July was officially recognized with the Nips providing the fireworks." A large destroyer opened up first, followed almost immediately by one of the heavy cruisers. One splash on the starboard quarter and three more on the port, all within 100 yards, precipitated quite a scramble on the bridge. Parche initiated a crash dive and as the conning tower hatch was going under the second salvo landed The Japanese dropped depth charges and patrolled the area for the next 20 minutes before clearing out at a brisk 24 knots. One crewman said that he lost count of the number of depth charges dropped at 70.

July 18th started with a convoy report from another submarine wolf pack. Parche, Steelhead, and Hammerhead, plotted and started an intercept course to the convoy. At 1300 a submariners dream come true was sighted — an escort carrier with no air cover or surface escorts. Before an attack could be delivered however, the carrier launched planes and began running away. Sonar heard several explosions indicating another wolf pack had gotten into the convoy the carrier was providing coverage for. A typhoon moving into the region began to degrade attack conditions so much that it became impossible to maintain periscope depth. The typhoons fury peaked on July 21st, and had cleared by the next day leaving the three subs alone in the area.

On July 26th, Group Commander Parks sent a message to Captain Wilkins of "Wilkin’s Wildcats", suggesting a joint patrol of the Balintang Channel by both wolf packs. Arriving in the area later that day Parche heard three heavy explosions and saw a huge column of white smoke rising at least 500 feet from one of the four vessels that had been sunk in the area that day.

On July 28th, Hammerhead, departed the area for Australia. The next day, Steelhead sighted a convoy, notified Parche of their location, track and speed, and gave chase through the afternoon and into the night. Steelhead closed in sinking a 4,471-ton cargo ship and a 10,238-ton tanker. During this daring night surface action Parche worked her way in inside two escorts and began an approach on a medium AK (armed amphibious transport) at 0354. The target slid by about 200 yards away and then turned to avoid two torpedoes Parche had fired at her. That move effectively blocked an escort who had sneaked in behind her and also opened up an opportunity for shots at two tankers and the AK. A stern shot took care of the cargo carrier and four bow tubes knocked out a tanker. Ramage ordered "Right-Full Rudder" to bring the stern tubes to bear on the second oiler and fired three torpedoes. One missed ahead of the ship but the other two fish hit the forward section slowing down the tanker but not stopping her completely.

The convoy, in an effort to escape the oncoming Steelhead also changed course. The escorts opened up with deck guns, machineguns and flares firing in all directions. The convoy started to mill about smartly with Parche in the middle. Suddenly a medium sized merchant-man with a sizeable superstructure came in sight. The torpedo reload crews forward and aft reloaded tubes as fast as they could and Parche fired two tubes as soon as the outer doors were opened. The two torpedoes broke the merchant-mans back, which sent her down within a couple of minutes.

With the merchant-man out of the way Parche came back after the first tanker to finish her off. Parche crossed her track astern at only 200 yards. At 500 yards the tanker opened up on Parche with everything she had, but her trim down by the bow kept her from depressing her guns enough to do any good. The small arms fire was peppering the bridge enough that Ramage sent all hands below except the quartermaster, who stuck to the after TBT until he had the set-up. At 800 yards Parche fired three torpedoes from the stern tubes at the tanker. All hit the tanker with terrific explosions effectively silencing the gunfire from that quarter. With five torpedoes in her the big tanker gave and went down leaving only a small oil fire.

The two escorts on the port quarter were now concentrating their machine gun fire on Parche. Ramage was about to come right to put them astern and head for the prize of the evening, a huge transport, when she spotted a ship coming in sharp on the starboard bow apparently intent on ramming. Ordering a full bell, Ramage sent the boat shooting across in front of the on-rushing enemy, then halfway across its track he ordered "Right-Full Rudder" swinging right the stern of the boat out of its path. The Japanese were screaming like a bunch of wild pigs as Parche barely missed being rammed by less than 50 feet. All hands exchanged mutual cheers and jeers.

Parche, now boxed in on both sides by several small craft and the big transport dead ahead had no alternative but to fire straight down the transports throat. The first fish started off to the right, so Ramage checked fire, spotted on, and fired two more. These were right in the groove and both hit the transport stopping her cold. Closing in on her starboard bow, the Parche swung hard left and fired one stern shot at 800 yards for a bull’s eye.

Stopping to take account of the situation, Ramage counted eight ships still visible on the JK RADAR screen. The bewildered escorts were still busy firing weapons in the darkness at Parche and at each other. The big transport was stopped and down by the bow, but showed no further signs of going down. Just as Parche started back to deliver the felling blow, the transport suddenly raised its stern into the air and went straight down, head first into the cold depths of the ocean. Parche then began an egress from the area yet one of the escorts continually challenged her with weapons fire amid the sounds of loud explosions in the darkness. The entire attack took 46 minutes. 

When Parche was finished, she had gotten the Japanese ships to open fire at one another, and had sunk a 10,238 ton tanker, a 4,471 ton passenger-cargo ship, damaged several thousand tons of Japanese ships ,and had disrupted yet another convoy. She also worked together with Steelhead in sinking an 8,990 ton transport. Steelhead sank two other ships, a transport and a cargo vessel. What made this more incredible was that this all occurred from the middle of a convoy of ships, on the surface, and at night.  For this action Parche received the Presidential Unit Citation. Commander Ramage was awarded the Congressional Medal of Honor. 

Q. D. Brown, PhM1c, had been suffering from acute attacks of appendicitis since July 15th, and so on August 1st, the sub departed for Saipan where she moored in Tanapag Harbor along side the USS Holland on August 5th to transfer her patient (Parche was the first allied submarine to enter Tanapag Harbor since the beginning of World War Two). The Holland treated the Parche crew royally with fresh fruit, ice cream, new magazines, and even a band. The crew had hoped for some well deserved liberty, but sounds of snipers could be heard on the beach. The crew decided to forego liberty, and the boat got underway the next day for Pearl Harbor, arriving there on August 16th.

Parche was credited with the following damage of enemy ships.