Hiršal was widely regarded as one of the most important Czech authors of experimental poetry; after early surrealistic writings, he made his literary debut with a collection of poems. Later on, he joined the group of artists around Jiri Kolar, a friend of whom he remained for his entire life and with whom he published children's books in the 1950s after having been forbidden any kind of work during the Soviet occupation. He later on signed the Charta 77.
In the 1960s, Hiršal he started writing experimental poetry with partner Bohumila Grögerová; the couple also co-authored several books. Furthermore, Josef Hiršal built a reputation as a translator of foreign works into the Czech language, translating the works of, among others, Christian Morgenstern, Ernst Jandl, Eugène Ionesco, Wolfgang Hildesheimer, Hans Magnus, Franz Kafka, Edgar Allan Poe, Heinrich Heine, H. C. Artmann, Helmut Heissenbüttel, Fernando Pessoa and Torquato Tasso; in 1989, he received the Austrian "Großer Österreichischer Staatspreis" for his translations.
Josef Hiršal died in September 2003 following an accident with the Prague tram in May in which he was seriously injured.