A-26s began arriving in Europe in late September 1944 for assignment to the Ninth Air Force. The initial deployment involved 18 aircraft and crews assigned to the 553d Squadron of the 386th Bomb Group. This unit flew its first mission on 6 September 1944. The first group to fully convert to the A-26B was 416th Bombardment Group with which it entered combat on 17 November, and the 409th Bombardment Group, whose A-26s became operational in late November. Due to a shortage of A-26C variants, the groups flew a combined A-20/A-26 unit until deliveries of the glass-nose version caught up. Besides bombing and strafing, tactical reconnaissance and night interdiction missions were undertaken successfully. In contrast to the Pacific-based units, the A-26 was well received by pilots and crew alike, and by 1945, the 9th AF had flown 11,567 missions, dropping 18,054 tons of bombs, recording seven confirmed kills while losing 67 aircraft.

Postwar era
The USAF Strategic Air Command had the renamed B-26 (RB-26) in service from 1949 through 1950, the Tactical Air Command through the late 1960s, and the last examples in service with the Air National Guard through 1972. The US Navy also used a small number of these aircraft in their utility squadrons for target towing and general utility use until superseded by the DC-130A variant of the C-130 Hercules. The Navy designation was JD-1 and JD-1D until 1962, when the JD-1 was redesignated UB-26J and the JD-1D was redesignated DB-26J.

Korean War
B-26 Invaders of the 3d Bombardment Group, operating from bases in Southern Japan, were some of the first USAF aircraft engaged in the Korean War, carrying out missions over South Korea on 27 and 28 June, before carrying out the first USAF bombing mission on North Korea on 29 June 1950 when they bombed an airfield outside of Pyongyang.

On 10 August 1950, the 452nd Reserve Bomb Wing was activated for Korean Service. This was the first time that an entire air force unit had ever been activated. It flew its first missions in November 1950 from Itazuke Japan doing daylight support with the 3rd Bomb Wing flying night missions. Because of the Chinese intervention it was forced to find another base and moved to Miho Air base on the west coast of Honshu-. In early 1951 it moved to East Pusan Air Base and continued its daylight as well as night intruder missions. In June 1951, it joined the 3rd Bomb Wing in night activity only, dividing the target areas with the 452nd taking the eastern half and the 3rd the western. For its efforts in the Korean War, it was awarded 2 Unit Citations and the Korean Presidential Citation. It also received credit for eight Campaign Operations. In May 1952 it was inactivated and all of its aircraft and equipment along with its regular air force personnel were absorbed by the 17th Bomb Wing. During its time as an active unit, the 452nd flew 15,000 sorties (7000 at night) with a loss of 85 crewmen.

B-26s were credited with the destruction of 38,500 vehicles, 406 locomotives, 3,700 railway trucks, and seven enemy aircraft on the ground. On 14 September 1951, Captain John S. Walmsley, Jr. attacked a supply train. When his guns jammed, he illuminated the target with his searchlight to enable his wingmen to destroy the train. Walmsley was shot down and posthumously awarded the Medal of Honor. Invaders carried out the last USAF bombing mission of the war 24 minutes before the Armistice Agreement was signed on 27 June 1953.

In addition to the standard attack versions of the B-26 which flew night interdiction missions, a small number of modified WB-26s and RB-26s of the 67th Tactical Reconnaissance Wing flew critical weather observation and reconnaissance missions in supporting roles.

First Indochina War
In the 1950s, the French Air Force's (Armée de l'air) Bombing Groups (Groupe de bombardement) including GB 1/19 Gascogne and GB 1/25 Tunisia used USAF-lent B-26 during the First Indochina War.

Cat Bi (Haiphong) based Douglas B-26 Invaders operated over Dien Bien Phu in March and April 1954 during the siege of Dien Bien Phu. In this period, a massive use of Philippines based USAF B-26s against the Viet Minh heavy artillery was planned by the U.S. and French Joint Chief of Staff as Operation Vulture, but was eventually cancelled by the respective governments.

Indonesia
In 1958, the CIA started Operation Haik in Indonesia, concerned about the Sukarno regime's communist leanings. At least a dozen B-26 Invaders were committed in support of rebel forces. On 18 May 1958, American contract pilot Allen Pope's B-26 was initially hit by anti-aircraft ground fire and then brought down by a North American P-51 Mustang flown by Capt. Ignatius Dewanto (the only known air-to-air kill in the history of the Indonesian Air Force). The capture and trial of Lieutenant Pope brought a quick end to Operation Haik, but the capabilities of the Invader were not lost on the Indonesian government. In 1959, the government purchased six aircraft at Davis-Monthan AFB and these were ferried to Indonesia in full military markings during mid-1960. These aircraft would have a long career and were utilized in a number of actions against rebels in various areas. The last operational flights of the three survivors was in 1976 supporting the Indonesian invasion of East Timor. In 1977, the last two flyers were retired.

Service with the USAF in Southeast Asia
The first B-26s to arrive in Southeast Asia were deployed to Takhli RTAFB, Thailand in December 1960. These unmarked aircraft, operated under the auspices of the U.S. CIA (Central Intelligence Agency), were soon augmented by an additional 16 aircraft, 12 B-26Bs and B-26Cs plus four RB-26Cs under Operation Mill Pond. The mission of all of these aircraft was to assist the Royal Lao Government in fighting the Pathet Lao. The repercussions from the Bay of Pigs invasion meant that no combat missions are known to have been flown, although RB-26Cs operated over Laos until the end of 1961. The aircraft were subsequently operated in South Vietnam under Project Farm Gate. The only other deployment of B-26 aircraft to Laos prior to the introduction of the B-26K/A-26A, was the deployment of two RB-26C aircraft, specifically modified for night reconnaissance, deployed to Laos between May and July 1962 under Project Black Watch. These aircraft, initially drawn from Farm Gate stocks, were returned upon the end of these missions.

The aircraft from Laos participated in the early phase of the Vietnam War with the USAF, but with Vietnamese markings as part of Project Farm Gate. Though Farm Gate operated B-26Bs, B-26Cs, and genuine RB-26Cs, many of these aircraft were operated under the designation RB-26C, though they were used in a combat capacity. During 1963, two RB-26C were sent to Clark AB in the Philippines for modifications, though not with night systems as with those modified for Black Watch. The two aircraft returned from Black Watch to Farm Gate were subsequently given the designation RB-26L to distinguish them from other modified RB-26C, and were assigned to Project Sweet Sue. Farm Gate's B-26s operated alongside the other primary strike aircraft of the time, the T-28 Trojan, before both aircraft types were replaced by the Douglas A-1 Skyraider. The B-26s were withdrawn from service in February 1964 after two accidents related to wing spar fatigue, one during combat in Southeast Asia in August 1963 and one during an airpower demonstration at Eglin AFB, Florida in February 1964.

On 11 February 1964, two pilots from the 1st Air Commando Wing stationed at Hurlburt Field, FL, died in the crash of a B-26 on Range 52 at Eglin AFB when it lost a wing during pull-out from a strafing pass. The aircraft was participating in a demonstration of the Special Air Warfare Center's counter insurgency capabilities and had completed a strafing run when the accident occurred. SAWC had presented the demonstration on an average of twice each month for the previous 21 months. B-26 aircraft used by USAF Commandos in Vietnam were grounded 8 April 1964, following an official investigation into the 11 February accident. B-26 aircraft in use by the Vietnamese Air Force were also grounded in accordance with the U.S. ruling.

In response to this, the On Mark Engineering Company of Van Nuys, California was selected by the Air Force to extensively upgrade the Invader for a counterinsurgency role. The first production flight of the B-26K was on 30 May 1964 at the Van Nuys Airport. On Mark converted 40 Invaders to the new B-26K Counter-Invader standard, which included upgraded engines, propellers, and brakes, re-manufactured wings, and wing tip fuel tanks, for use by the 609th Special Operations Squadron. In May 1966, the B-26K was re-designated A-26A/K for political reasons (Thailand did not allow the U.S. to have bombers stationed in country, so the Invaders were redesignated with an "A", for attack aircraft) and deployed in Thailand to help disrupt supplies moving along the Ho Chi Minh trail. Two of these aircraft were further modified with a Forward Looking Infrared (FLIR system) under project Lonesome Tiger, as a part of Operation Shed Light.

Bay of Pigs Invasion
In early 1961, about 20 B-26Bs, most converted from B-26C configuration, were 'sanitized' at Duke Field (aka Auxiliary Field Three at Eglin AFB). They had defensive armament removed, and were fitted with the eight-gun nose, underwing drop tanks, and rocket racks. They were flown to a CIA-run base in Guatemala where training was underway of B-26, C-46 and C-54 Cuban exile air crews by personnel from the Alabama ANG (Air National Guard). After transfer to Nicaragua in early April 1961, they were painted in the markings of the FAR (Fuerza Aérea Revolucionaria), the air force of the Cuban government. On 15 April 1961, crewed by Cuban exiles, eight B-26s of the FAL (Fuerza Aérea de Liberación) attacked three Cuban airfields, in an attempt to destroy FAR combat aircraft on the ground. On 17 April 1961, FAL B-26s supported the seaborne Bay of Pigs Invasion of Cuba. The conflict ended on 19 April, after the loss of nine FAL B-26s, 10 Cuban exiles and 4 American aircrew in combat. The FAR flew B-26Cs in the conflict, one of which was shot down by a CIA 'command ship' with the loss of 4 Cuban aircrew.

Africa in the 1960s
CIA contracted pilots, some previously employed during the Bay of Pigs Invasion, flew B-26Ks for ground attack against Simba rebels in the Congo Crisis. New production B-26K Counter-Invaders were delivered to the Congo via Hurlburt Field in 1964.

The Portuguese Air Force purchased Invaders covertly for use in Portuguese Angola in 1965, during the Portuguese Colonial War.

Biafra used two provisionally armed B-26s in combat during Nigerian Civil War in 1967, flown among others by Jan Zumbach.