Marek was born in Warsaw, as the only son of Maciej Hłasko and Maria Łucja, née Rosiak.

In the Hłasko family, children were baptised relatively late, hence the writer-to-be was baptized on 26 December 1935 in the Church of the Holy Redeemer in Warsaw.

"[3] At the outbreak of World War II, Hłasko's mother was working in the management secretariat of the City Power Station in Warsaw.

In March 1945, Maria and her son moved to Chorzów and two months later to Białystok, where she settled with Kazimierz Gryczkiewicz.

In the summer of 1946, Marek Hłasko joined the Bolesław Chrobry First Wrocław Scout Troops.

Marek worked as a messenger at the World Congress of Intellectuals for Peace, held in August 1948 in Wrocław.

In his biography of Hłasko, Andrzej Czyżewski writes: "(Marek) began his education at the age of six and a half.

Later, from December 1949 to January 1950, he attended the Technical and Drama High School in Warsaw, yet, in the end of December 1949 and early January 1950, he was expelled for "a notorious disrespect to school regulations, criminal violations, and wielding a corrupting influence on his colleagues".

Successively, he worked from 26 February to 15 April 1951 in an Equipment Base of the City's Construction Union, from 27 April 1951 to 16 June 1952 in a subway construction company "Metrobudowa", from 4 August to 1 December 1952 in a Transport Association of Warsaw Associations of Consumers, and till 30 March 1953 in a Warsaw Transport Enterprise of the City Retail Sale.

Hłasko became a correspondent for Trybuna Ludowa (a popular Polish daily) when he was working for "Metrobudowa".

His reply letter written on 3 December of the same year included a criticism of Hłasko's literary attempts, but also drew attention to the young author's talent.

Moreover, also in 1952, Hłasko followed Stefan Łoś's advice and established contact with the Polish Literary Association and Igor Newerly, who was the protector of young writers.

Hłasko introduced himself, to both Czeszko and Newerly, as "an uneducated driver who tries to describe his life in his free time after work".

Moreover, following Bohdan Czeszko's advice, he wrote a story based on his sketches (a final version of Baza Sokołowska) and finished a novel Sonata marymoncka.

He made his debut with Baza Sokołowska in Sztandar Młodych (a daily paper published in Poland in 1950–1997) in 1954.

In 1955–1957, he edited a prose section in Po Prostu (a Polish socio-political magazine published in 1947–57), but he was not a good publicist [how?].

The publication of Cmentarze [The Graveyard], a novel critical of state socialism, in the émigré Polish-language Parisian monthly Kultura, caused a negative press campaign to be launched against him back in Poland.

As he did not have a talent for languages [citation needed], he found it difficult to adjust to the reality of life abroad.

He had an affair with Betty Utey, the wife of Rebel Without a Cause director Nicholas Ray, ending his career as a screenwriter.

Jan Himilsbach, a writer, actor and stonecutter who worked at the cemetery, was one of the initiators for taking Hłasko's remains back to Poland.

He was a co-screenwriter of films such as Koniec nocy (1957), Pętla (1957), Spotkania (1957), Ósmy dzień tygodnia (1958) and Baza ludzi umarłych.