Jaroslav Blažek comes from Mariánské Lázně. As a child, he devoted himself to dance, which he later exchanged for acting, although he continues to make full use of his movement talent on stage. He studied acting at the Prague Conservatory, where, during his studies, he appeared in productions at the Theatre Studio, including Dog, Night and Knife and Punk Rock. In 2017, he graduated with his final-year role in the drama Terminus. Even then, he was already appearing as a guest on Prague stages, for example at the Vršovice theatre MANA in Mother and at ABC Theatre in Romeo and Juliet. Together with Martin Zahálka Jr., he founded the band Strohoskop during his studies, in which he performed as guitarist, singer and lyricist.
He gained his greatest popularity through the role of bartender Bruno in the television series Ulice (2017–2024). He also appeared in the series Rapl, Specialisté and in the comedy series Mužketýři. As co-author and actor, he contributed to the sketch show První dobrá (2022, Nova Fun/Voyo).
Since September 2022, he has been a permanent member of the ensemble of Divadlo pod Palmovkou, where he is one of the most frequently cast actors.
He is also involved in improvisation and regularly appears in the show Komikaze, a comedy improvisation performance in which young actors create stories on the spot based on suggestions from the audience. Their humour boldly reflects current social events and offers a fresh view of the world.