Tadeusz Lomnicki began his education in the theatre arts in 1945 when he enrolled in the Theatre Studio at the Stary Teatr in Krakow. In 1946 he spent a season at the Teatr Slaski in Katowice. He returned to Krakow in 1947, appearing on stage at both the Teatr im. Juliusza Slowackiego and the Stary Teatr. In 1949 he left for Warsaw, where he signed on with the Teatr Wspolczesny. Lomnicki would remain there until 1974, though during this period he performed occasionally at the National Theatre in Warsaw. He became a member of the Communist Party in 1951; during his initial years in Warsaw he also studied stage direction at the State Higher School of Theatre in Warsaw. He was awarded a directing degree in 1956. In 1970, he became the rector of the theatre school in Warsaw, retaining this position until 1981. In 1975, Lomnicki was elected a member of the Central Committee of the Communist Party. He was trusted by those in power at that time and received an opportunity to create his own theatre. His initiative lead to the creation in 1976 of the Teatr na Woli, which he headed until his resignation in 1981. At around the time he left the theatre, two days after Martial Law was declared in Poland, he handed in his Communist Party membership card. That same year he joined Warsaw's Teatr Polski, and in 1983/84 was an actor at the Teatr Studio in Warsaw. Throughout the 1980s and 1990s, he was not linked to any institutional theatre, instead making numerous guest appearances at a number of Warsaw theatres.

He had dreamed of playing the part of King Lear for a long time before he finally succeeded in mounting a production and going into rehearsal. He first asked noted translator and poet Stanislaw Baranczak to produce a new translation of the play. The translation in hand, he approached a number of directors about working with him on the production. Among those who turned him down at the time was Andrzej Wajda. Ultimately, Eugeniusz Korin agreed to direct the production at Poznan's Teatr Nowy. One week before the premiere, on February 22, 1992, Tadeusz Lomnicki passed away while rehearsing.