[1][2] On 30 March 1943, I-177 departed Kure, Japan, in company with her sister ship I-178 bound for Truk Atoll, which she reached on 7 April 1943.

[1][2] I-177 got underway from Truk on 10 April 1943, assigned a patrol area off the east coast of Australia together with I-178 and the submarine I-180.

[1][2] During the predawn hours of 14 May 1943, I-177, operating on the surface 40 nautical miles (74 km; 46 mi) east of Brisbane, sighted the 3,222-ton Australian hospital ship AHS Centaur 24 nautical miles (44 km; 28 mi) east-northeast of North Stradbroke Island.

[2][3] Centaur had departed Sydney, Australia, on 12 May 1943 bound for Port Moresby, New Guinea, via Cairns, Australia, to evacuate sick and wounded personnel during fighting in the New Guinea campaign,[2][4] and was steaming northward in darkness[4] displaying the lights and markings required of a hospital ship in wartime under the Hague Convention,[5] I-177 nonetheless submerged to periscope depth and fired a torpedo at Centaur at 04:10 which struck her at 04:15.

[2] Centaur′s survivors drifted until 15 May 1943, hearing I-177′s diesel engines as she passed through the area of the sinking again on the surface in the early-morning darkness of 15 May, before a Royal Australian Air Force Avro Anson patrol aircraft sighted them clinging to debris.

[2][8] The United States Navy destroyer USS Mugford (DD-389) departed Brisbane to come to their assistance, arriving on the scene at 14:00 on 15 May and pulling them from the water.

Nakagawa survived the war and refused to speak on the subject of the sinking of Centaur, even to defend himself.

However, Nakagawa was charged with ordering the machine-gunning of survivors from torpedoed ships on three different dates in February 1944 while in command of the submarine I-37.

On 13 September, she received orders to divert to attack Allied landing forces at Finschhafen, New Guinea, but she found no targets there and resumed her voyage to Lae.

[2] She unloaded her cargo and put back to sea, where during the evening of 14 September she detected the propeller noises of what her crew assessed as several U.S. Navy destroyers at a range of a few thousand yards while she was on the surface.

[2] Assuming that the destroyers had detected her on radar, she submerged to her test depth of 100 meters (328 ft) to await a depth-charge attack, but none came.

[1][2] In the immediate aftermath of the Battle of Cape St. George, fought on the night of 24–25 November 1943 in the waters between Buka Island and Cape St. George on New Ireland, I-177 got underway from Rabaul on 25 November to search for survivors of the sunken destroyer Yugiri; she rescued 279 men and the submarine I-181 rescued 11.

[2] A daihatsu barge came alongside and began loading cargo from I-177, and a boat set out from shore carrying the commander of the 18th Army, General Hatazō Adachi, the commander of the 7th Base Unit, Rear Admiral Kyuhachi Kudo, and ten of their staff officers.

[2] After taking Adachi and Kudo and their staffs aboard, she left Sio for the last time and proceeded to Madang, New Guinea, where her passengers disembarked at around 12:00 on 11 January 1944.

[1][2] She again put to sea from Ōminato on 8 June 1944 to conduct a war patrol in the North Pacific east of the Kuril Islands.

[2] On 19 September 1944, I-177 departed Kure, Japan, with the commander of Submarine Division 34 embarked to conduct a war patrol off the Palaus, off Halmahera in the Japanese-occupied Netherlands East Indies, and off Mindanao in the Philippine Islands.

[1][2] When she arrived in her patrol area off the Palaus on 24 September 1944, she received orders to reconnoiter Ulithi Atoll in the Caroline Islands.

[2] The Mariner dropped a Mark 24 FIDO acoustic homing torpedo which inflicted heavy damage on I-177.

[2] The Mariner then passed I-177′s position to a nearby hunter-killer group centered around the escort aircraft carrier USS Hoggatt Bay (CVE-75), which began a search for I-177.

[2] Hoggatt Bay was north-northeast of Angaur at 03:11 on 3 October 1944 when she made radar contact on I-177 at a range of 20,000 yards (18,300 m).

[2] On 18 November 1944, the Imperial Japanese Navy declared her to be presumed lost with all hands in the Palaus area.