Following the end of the war and the integration of Białystok into the newly established Polish People's Republic, it was reopened on September 10, 1944.

In the autumn and winter of 1944/1945, the prison was protected by NKVD units, and some of its premises were given over to the counterintelligence SMERSH of the 2nd Belorussian Front.

[3] In the common room of the administrative building of the prison in Białystok, court hearings were held, during which various sentences were passed, including the death penalty.

From the turn of 1946/1947 the sentences were carried out by individual executioners - prison officers using handguns (the so-called Katyn method), in the same basement of the administrative building.

[5] The facility's highest population in post-war period took place in 1950, when it held about two thousands prisoners.