On 4 March 1945, the city was captured by the Red Army.
Under the border changes forced by the Soviet Union in the post-war Potsdam Agreement, Koszalin became part of Poland as part of the so-called Recovered Territories.
The city's German population that had not yet fled was expelled to the remainder of post-war Germany in accordance to the Potsdam Agreement.
The city was resettled by Poles and Kashubians, many of whom had been expelled from Polish territory annexed by the Soviets.

As early as March 1945 a Polish police unit was established, consisting of former forced labourers and prisoners of war, however, the Soviets, still present in the city, plundered local industrial factories in April.
From May 1945, life in the destroyed city was being organized, the first post-war schools, shops and service premises were established.
In 1946, the first public library was opened, whose director was later Maria Pilecka, the sister of Polish national hero Witold Pilecki.
In March 1946, the anti-communist Home Army 5th Wilno Brigade was active in Koszalin.
In July 1947, the last units of the Soviet Army left Koszalin, and from that time only Polish troops were stationed in the city.
In 1953 a local radio station was founded in Koszalin.

Initially, Koszalin was the first post-war regional capital of Polish Western Pomerania, before the administration finally moved to Szczecin in February 1946, after which the region was named the Szczecin Voivodeship.
In 1950 this voivodeship was divided into a truncated Szczecin Voivodeship and Koszalin Voivodeship.
In years 1950-75 Koszalin was the capital of the enlarged Koszalin Voivodeship sometimes called Middle Pomerania due to becoming the fastest growing city in Poland.
In years 1975-98 it was the capital of the smaller Koszalin Voivodeship.
As a result of the Local Government Reorganization Act (1998) Koszalin became part of the West Pomeranian Voivodeship (effective 1 January 1999) regardless of an earlier proposal for a new Middle Pomeranian Voivodeship covering approximately the area of former Koszalin Voivodeship (1950–75).

In 1991, Koszalin was visited by Pope John Paul II.
On the fifth anniversary of his visit, his monument was unveiled in the city center.
On 4 March 1945, the city was captured by the Red Army. Under the border changes forced by the Soviet Union in the post-war Potsdam Agreement, Koszalin became part of Poland as part of the so-called Recovered Territories. The city's German population that had not yet fled was expelled to the remainder of post-war Germany in accordance to the Potsdam Agreement. The city was resettled by Poles and Kashubians, many of whom had been expelled from Polish territory annexed by the Soviets.
As early as March 1945 a Polish police unit was established, consisting of former forced labourers and prisoners of war, however, the Soviets, still present in the city, plundered local industrial factories in April. From May 1945, life in the destroyed city was being organized, the first post-war schools, shops and service premises were established. In 1946, the first public library was opened, whose director was later Maria Pilecka, the sister of Polish national hero Witold Pilecki. In March 1946, the anti-communist Home Army 5th Wilno Brigade was active in Koszalin. In July 1947, the last units of the Soviet Army left Koszalin, and from that time only Polish troops were stationed in the city. In 1953 a local radio station was founded in Koszalin.
Initially, Koszalin was the first post-war regional capital of Polish Western Pomerania, before the administration finally moved to Szczecin in February 1946, after which the region was named the Szczecin Voivodeship. In 1950 this voivodeship was divided into a truncated Szczecin Voivodeship and Koszalin Voivodeship. In years 1950-75 Koszalin was the capital of the enlarged Koszalin Voivodeship sometimes called Middle Pomerania due to becoming the fastest growing city in Poland. In years 1975-98 it was the capital of the smaller Koszalin Voivodeship. As a result of the Local Government Reorganization Act (1998) Koszalin became part of the West Pomeranian Voivodeship (effective 1 January 1999) regardless of an earlier proposal for a new Middle Pomeranian Voivodeship covering approximately the area of former Koszalin Voivodeship (1950–75).
In 1991, Koszalin was visited by Pope John Paul II. On the fifth anniversary of his visit, his monument was unveiled in the city center.
Koszalin