Born in Wegeleben (now in Saxony-Anhalt) in the Kingdom of Prussia in the German Empire, Bormann was the son of Theodor Bormann (1862–1903), a post office employee, and his second wife, Antonie Bernhardine Mennong.

Bormann's studies at an agricultural trade high school were interrupted when he joined the 55th Field Artillery Regiment as a gunner in June 1918, in the last days of World War I.

He never saw action, but served garrison duty until February 1919.

Bormann joined the Freikorps organisation headed by Gerhard Roßbach in 1922, acting as section leader and treasurer.

In 1927, Bormann joined the National Socialist German Workers Party (Nazi Party; NSDAP). His membership number was 60,508.

On 2 September 1929, Bormann married 19-year-old Gerda Buch, whose father, Major Walter Buch, served as a chairman of the Untersuchung und Schlichtungs-Ausschuss (USCHLA; Investigation and Settlement Committee), which was responsible for settling disputes within the party. Hitler was a frequent visitor to the Buch house, and it was here that Bormann met him. Hess and Hitler served as witnesses at the wedding.

Initially the NSDAP provided coverage through insurance companies for members who were hurt or killed in the frequent violent skirmishes with members of other political parties. As insurance companies were unwilling to pay out claims for such activities, in 1930 Bormann set up the Hilfskasse der NSDAP (NSDAP Auxiliary Fund), a benefits and relief fund directly administered by the party.

After the Machtergreifung (NSDAP seizure of power) in January 1933, the relief fund was repurposed to provide general accident and property insurance, so Bormann resigned from its administration.

Bormann applied for a transfer and was accepted as chief of staff in the office of Rudolf Hess, the Deputy Führer, on 1 July 1933.

Bormann served as personal secretary to Hess from 4 July 1933 until May 1941.

On 10 October 1933 Hitler named Bormann Reichsleiter (national leader – the highest party rank) of the NSDAP.

By June 1934, Bormann was gaining acceptance into Hitler's inner circle and accompanied him everywhere, providing briefings and summaries of events and requests.

In 1935, Bormann was appointed as overseer of renovations at the Berghof, Hitler's property at Obersalzberg.

He joined the Schutzstaffel (SS) on 1 January 1937 with number 278,267.

Bormann was one of the leading proponents of the ongoing persecution of the Christian churches. In February 1937, he decreed that members of the clergy should not be admitted to the NSDAP.

By special order of Heinrich Himmler in 1938, Bormann was granted SS number 555 to reflect his Alter Kämpfer (Old Fighter) status.

Bormann travelled everywhere with Hitler, including trips to Austria in 1938 after the Anschluss (the annexation of Austria into Nazi Germany), and to the Sudetenland after the signing of the Munich Agreement later that year.

Bormann was placed in charge of organising the 1938 Nuremberg Rally, a major annual party event.

In 1938, Bormann ruled that any members of the clergy who were holding party offices should be dismissed, and that any party member who was considering entering the clergy had to give up his party membership.

He moved to Munich in October 1928, where he worked in the SA insurance office.

In 1941 the Catholic Bishop of Münster, Clemens August Graf von Galen, publicly protested against the persecution and against Action T4, the Nazi involuntary euthanasia programme under which the mentally ill, physically deformed, and incurably sick were to be killed. In a series of sermons that received international attention, he criticised the programme as illegal and immoral. His sermons led to a widespread protest movement among church leaders, the strongest protest against a Nazi policy up until that point.

Hess was concerned that Germany would face a war on two fronts as plans progressed for Operation Barbarossa, the invasion of the Soviet Union scheduled to take place later that year. He flew solo to Britain on 10 May 1941 to seek peace negotiations with the British government. He was arrested on arrival and spent the rest of the war as a British prisoner.

Hitler considered Hess' departure a personal betrayal, and ordered Hess to be shot should he return to Germany and abolished the post of Deputy Führer on 12 May 1941, assigning Hess' former duties to Bormann, with the title of Head of the Parteikanzlei (Party Chancellery). In this position he was responsible for all NSDAP appointments, and was answerable only to Hitler. Associates began to refer to him as the "Brown Eminence", although never to his face.

Bormann was invariably the advocate of extremely harsh, radical measures when it came to the treatment of Jews, the conquered eastern peoples, and prisoners of war. He signed the decree of 31 May 1941 extending the 1935 Nuremberg Laws to the annexed territories of the East.

Knowing Hitler viewed Slavic people as inferior, Bormann opposed the introduction of German criminal law into the conquered eastern territories. He lobbied for and eventually achieved a strict separate penal code that implemented martial law for the Polish and Jewish inhabitants of these areas. The "Edict on Criminal Law Practices against Poles and Jews in the Incorporated Eastern Territories", promulgated 4 December 1941, permitted corporal punishment and death sentences for even the most trivial of offences.

Bormann signed the decree of 9 October 1942 prescribing that the permanent Final Solution in Greater Germany could no longer be solved by emigration, but only by the use of "ruthless force in the special camps of the East", that is, extermination in Nazi death camps.

Bormann's power and effective reach broadened considerably during the war. By early 1943, the war produced a labour crisis for the regime. Hitler created a three-man committee with representatives of the State, the army, and the Party in an attempt to centralise control of the war economy. The committee members were Hans Lammers, Field Marshal Wilhelm Keitel and Bormann, who controlled the Party.

Preoccupied with military matters and spending most of his time at his military headquarters on the eastern front, Hitler came to rely more and more on Bormann to handle the domestic policies of the country. On 12 April 1943, Hitler officially appointed Bormann as Personal Secretary to the Führer. By this time Bormann had de facto control over all domestic matters, and this new appointment gave him the power to act in an official capacity in any matter.

A further decree, signed by Bormann on 1 July 1943, gave Adolf Eichmann absolute powers over Jews, who now came under the exclusive jurisdiction of the Gestapo.

Bormann and Himmler shared responsibility for the Volkssturm (people's militia), which drafted all remaining able-bodied men aged 16 to 60 into a last-ditch militia founded on 18 October 1944. Poorly equipped and trained, the men were sent to fight on the eastern front, where nearly 175,000 of them were killed without having any discernible impact on the Soviet advance.

Hitler transferred his headquarters to the Führerbunker ("Leader's bunker") in Berlin on 16 January 1945, where he (along with Bormann, his secretary Else Krüger, and others) remained until the end of April.

The Battle of Berlin, the final major Soviet offensive of the war, began on 16 April 1945.

By 19 April the Red Army started to encircle the city.

On 20 April, Hitler's 56th birthday, he made his last trip to the surface. In the ruined garden of the Reich Chancellery, he awarded Iron Crosses to boy soldiers of the Hitler Youth. That afternoon, Berlin was bombarded by Soviet artillery for the first time.

On 23 April, Albert Bormann left the bunker complex and flew to the Obersalzberg. He and several others had been ordered by Hitler to leave Berlin.

Gerda Bormann and the children fled Obersalzberg for Italy on 25 April 1945 after an Allied air attack.

In the early morning hours of 29 April 1945, Wilhelm Burgdorf, Goebbels, Hans Krebs, and Bormann witnessed and signed Hitler's last will and testament. Bormann was named executor of the estate. That same night, Hitler married Eva Braun in a civil ceremony.

As Soviet forces continued to fight their way into the centre of Berlin, Hitler and Braun committed suicide on the afternoon of 30 April. Braun took cyanide and Hitler shot himself. Pursuant to Hitler's instructions, their bodies were carried up to the Reich Chancellery garden and burned.

In accordance with Hitler's last wishes, Bormann was named as Party Minister, thus officially confirming his top position in the Party. Grand Admiral Karl Dönitz was appointed as the new Reichspräsident (President of Germany) and Goebbels became head of government and Chancellor of Germany. Goebbels and his wife Magda committed suicide later that day.

At around 11:00 pm on 1 May, Bormann left the Führerbunker with SS doctor Ludwig Stumpfegger, Hitler Youth leader Artur Axmann, and Hitler's pilot Hans Baur as members of one of the groups attempting to break out of the Soviet encirclement. Bormann carried with him a copy of Hitler's last will and testament.

Bormann's group left the Führerbunker and travelled on foot via a U-Bahn tunnel to the Friedrichstraße station, where they surfaced. Several members of the party attempted to cross the Spree River at the Weidendammer Bridge while crouching behind a Tiger tank. The tank was hit by Soviet artillery and destroyed, and Bormann and Stumpfegger were knocked to the ground. Bormann, Stumpfegger, and several others eventually crossed the river on their third attempt. Bormann, Stumpfegger, and Axmann walked along the railway tracks to Lehrter station, where Axmann decided to leave the others and go in the opposite direction. When he encountered a Red Army patrol, Axmann doubled back. He saw two bodies, which he later identified as Bormann and Stumpfegger, on a bridge near the railway switching yard. He did not have time to check thoroughly, so he did not know how they died. Since the Soviets never admitted to finding Bormann's body, his fate remained in doubt for many years.

On 2 May, the Battle in Berlin ended when General der Artillerie Helmuth Weidling, the commander of the Berlin Defense Area, unconditionally surrendered the city to General Vasily Chuikov, the commander of the Soviet 8th Guards Army.

The trial got underway on 20 November 1945. Lacking evidence confirming Bormann's death, the International Military Tribunal tried him in absentia, as permitted under article 12 of their charter. He was charged with three counts: conspiracy to wage a war of aggression, war crimes, and crimes against humanity.

Gerda Bormann died of cancer on 26 April 1946, in Merano, Italy. Bormann's children survived the war, and were cared for in foster homes.

On 15 October 1946 he was sentenced to death by hanging, with the provision that if he were later found alive, any new facts brought to light at that time could be taken into consideration to reduce the sentence or overturn it.

In 1963, a retired postal worker named Albert Krumnow told police that around 8 May 1945 the Soviets had ordered him and his colleagues to bury two bodies found near the railway bridge near Lehrter station. One was dressed in a Wehrmacht uniform and the other was clad only in his underwear.

In 1964, the West German government offered a reward of 100,000 Deutsche Marks for information leading to Bormann's capture.

Excavations on 20-21 July 1965 at the site specified by Axmann and Krumnow failed to locate the bodies.

The West German government declared that its hunt for Bormann was over in 1971.

On 7 December 1972, construction workers uncovered human remains near Lehrter station in West Berlin just 12 m (39 ft) from the spot where Krumnow claimed he had buried them. Forensic examiners determined that the size of the skeleton and the shape of the skull were identical to Bormann's. Likewise, the second skeleton was deemed to be Stumpfegger's, since it was of similar height to his last known proportions. Composite photographs, where images of the skulls were overlaid on photographs of the men's faces, were completely congruent.

Facial reconstruction was undertaken in early 1973 on both skulls to confirm the identities of the bodies. Soon after, the West German government declared Bormann dead. The family was not allowed to cremate the body, in case further forensic examination later provided necessary.

The remains were conclusively identified as Bormann's in 1998 when German authorities ordered genetic testing on fragments of the skull. The testing was led by Wolfgang Eisenmenger, Professor of Forensic Science at Ludwig Maximilian University of Munich. Tests using DNA from one of his relatives identified the skull as that of Bormann.

Bormann's remains were cremated and his ashes were scattered in the Baltic Sea on 16 August 1999.