[1] Following the liberation, he took up a career as a professional actor in the avant-garde studio Větrník (from 1945 to 1946), and afterward he was engaged in many Prague theatre scenes.

In the mid-1980s Kopecký acted in a politically biased documentary film about emigrants, but, on the other side, he presented a very critical speech against the communist régime in May 1987, at the Fourth Congress of Dramatic Artists.

[2] For many years Kopecký suffered from manic-depressive disease, partially caused by the death of his mother, who perished in a concentration camp.

[2] Among his most valued roles were Paolino in Pirandello's The Man, The Beast and The Virtue, Professor Higgins in G. B. Shaw's Pygmalion, Harpagon in Molière's The Miser, and many others.

[2] Among his most valued roles in film were Chaplain Katz in The Good Soldier Švejk (1956), Hogofogo in Limonádový Joe (1964), the chief of the Czech water-goblins in Jak utopit dr. Mráčka aneb Konec vodníků v Čechách (1974), the villainous Count von Kratzmar in Adéla ještě nevečeřela (1977), and many others.