Between 1916 and 1924, Werich attended "reálné gymnasium" (equivalent to high school) in Křemencova Street in Prague (where his future business partner, Jiří Voskovec, also studied). He studied law at the Charles University Law School from 1924 to 1927, from which he made an early departure to begin his artistic career and forge one of the most important partnerships of his life.

For more than 10 years he worked in theatre Jiří Voskovec and Jaroslav Ježek. Their partnership was a platform for their numerous left-wing political satires, most notably in the Osvobozené divadlo (Liberated Theatre). The trio's work took inspiration from Dada, with its love of the absurd, a reaction against bourgeois values and the horrors of World War I.

In 1955 he begun working in cinema, and 1960s were a peak in his actor career. From the creation of the ABC Theatre he moved to the City Theatres of Prague and then to the Musical Theatre of Karlin and Nusle. Werich was originally cast by producer Harry Saltzman to play Ernst Stavro Blofeld in the 1967 James Bond film You Only Live Twice. Upon his arrival at the Pinewood set, both producer Albert R. Broccoli and director Lewis Gilbert felt that he was a poor choice, resembling a "poor, benevolent Santa Claus".