Little information about his private life has survived. He was born into a Catholic family in Bavaria. After finishing school, he worked in an ironworks. By the time he was committed to serving in the SS, he had married and had two children. In 1926, at the age of 21, he donned a brown shirt when he joined the SA (from German: Sturmabteilung), the assault troops of the NSDAP. In Weiden, where he was from, he formed local SA and Hitlerjugend structures with friends. He was one of the first members of the NSDAP. At the same time, he began studying electrical engineering, graduating in 1930. He worked as an assistant at the school, but was dismissed from it after a while.

Weiss decided to tie his future to the SS. He joined the organization in 1932. Given the course of his career, one can guess that, like many later concentration camp commanders, he joined the Dead Skull Squad – SS-Totenkopfverbände, organized by Theodor Eicke. In the spring of 1933, he became a guard at the Dachau concentration camp. A few months later, thanks to his specialized training, he became an engineer in the same camp for more than five years, and then adjutant to the subsequent Dachau commandants Hans Lortiz and Alex Piotrowski.

Martin Weiss must have been recognized for his contribution to the Third Reich during his service at Dachau, because already after the outbreak of World War II he was ordered to organize the Neuengamme concentration camp. Neuengamme was the site where Zyklon B was tested for possible use on prisoners. Martin Weiss was also tasked with expanding the Arbeitsdorf concentration camp, to which 800 prisoners from Neuengamme were transferred. This camp was established near Wolfsburg, and the prisoners there were to provide cheap labor for the construction of the new Volkswagen car, which was cheap and available to all Germans. At the time, Weiss held simultaneous authority over both camps.

Oswald Pohl, head of the SS Main Economic and Administrative Office, wanted the conditions of the prisoners in the camps to improve. He did not do this for moral reasons, for he believed that better conditions would ensure that the prisoners would live longer, and that German industry would therefore be able to use them as free labor for longer. Therefore, when Weiss was given the position of commandant of the Dachau camp in 1942, he was heavily criticized by Pohl for the conditions in the camp. Weiss complied with Pohl’s orders, but the terror in the camp continued. When Weiss served as commandant from 1942 to the end of 1943, dozens of death sentences were carried out. During the post-war trial of the Dachau camp staff, Weiss explained that these were death sentences on Gestapo prisoners, which were carried out on Himmler’s orders.

From this period, when Weiss was first commandant of Dachau, come accounts saying that conditions had improved in the camp. Among other things, beatings were banned, and food parcels were allowed to be sent to prisoners.

Weiss was sent to the Lublin camp the day after the massacre, the so-called Aktion Erntefest, when more than 17,000 people were murdered at Majdanek in one day on November 3. Weiss took it upon himself to control the situation after the massacre. Martin Weiss commanded Majdanek until April 1944.

He was then sent to the Muhldorf sub-camp, where Luftwaffe drifts were established using prisoner labor. Faced with the collapse of the front and the approach of the Americans, Weiss, who found himself back in Dachau, allegedly urged the surrender of the camp to the Allies, denying Himmler’s orders to burn the camp and obliterate all traces of criminal activity. However, the day before the Americans entered, Weiss escaped from Dachau. A day later, he was arrested in Munich.

At the trial of the Dachau staff, which took place in November/December 1945, Weiss was found guilty of crimes against humanity for acts committed during his tenure as commandant of Dachau and the other camps. He was sentenced to death, and the verdict was carried out on May 29, 1946.