The PBJ-1 was a navalized version of the USAAF B-25. It had its origin in a deal cut in mid-1942 between the Navy and the USAAF. As part of the deal, 50 B-25Cs and 152 B-25Ds were transferred to the Navy from the USAAF. The bombers carried Navy serial numbers beginning with 34998. The first PBJ-1s arrived in February 1943. They were used by Marine Corps pilots, beginning with VMB-413. Many of them were equipped with a search radar with a retractable radome fitted in place of the ventral turret.

Large numbers of B-25H and J variants were delivered to the Navy as PBJ-1H and PBJ-1J respectively. These aircraft joined, but did not necessarily replace, the earlier PBJs.

The PBJs were operated almost exclusively by the Marine Corps as land-based bombers. To operate them, the U.S. Marine Corps established a number of bomber squadrons, beginning with VMB-413, in March 1943 at Cherry Point, North Carolina. Eight VMB squadrons were flying PBJs by the end of 1943, forming the initial Marine Medium Bombardment Group. Four more squadrons were in the process of formation in late 1945, but had not yet deployed by the time the war ended.

Operational use of the Marine Corps PBJ-1s began in March 1944. The Marine PBJs operated from the Philippines, Saipan, Iwo Jima and Okinawa during the last few months of the Pacific war. Their primary mission was the long range interdiction of enemy shipping that was trying to run the blockade which was strangling Japan. The weapon of choice during these missions was usually the five-inch HVAR rocket, eight of which could be carried on underwing racks. Many of the PBJ-1C and D versions carried a rather ugly, bulbous antenna for an APS-3 search radar sticking out of the upper part of the transparent nose. On the PBJ-1H and J, the APS-3 search radar antenna was usually housed inside a ventral or wingtip radome. Some PBJ-1Js had their top turrets removed to save weight, especially toward the end of the war when Japanese fighters had become relatively scarce.

After World War Two, some PBJs were stationed at the Navy's rocket laboratory at Inyokern, California to test various air to ground rockets and arrangements; including a twin barrel nose arrangement that could fire ten spin stabilized 5 inch rockets in one salvo

U.S. Navy / U.S. Marine Corps variants

PBJ-1C

Similar to the B-25C for the U.S. Navy; often fitted with airborne search radar and used in the anti-submarine role.

PBJ-1D

Similar to the B-25D for the U.S. Navy and U.S. Marine Corps. Differed in having a single .50 in (12.7 mm) machine gun in the tail turret and waist gun positions similar to the B-25H. Often fitted with airborne search radar and used in the anti-submarine role.

PBJ-1G

U.S. Navy/U.S. Marine Corps designation for the B-25G

PBJ-1H

U.S. Navy/U.S. Marine Corps designation for the B-25H.  One PBJ-1H was modified with carrier take-off and landing equipment and successfully tested on the USS Shangri-La, but the Navy did not continue development.

PBJ-1J

U.S. Navy designation for the B-25J-NC (Blocks −1 through −35) with improvements in radio and other equipment. Often fitted with "package guns" and wingtip search radar for the anti-shipping/anti-submarine role.