Vennberg became known for translating and introducing the literary works by Franz Kafka to Swedish, including The Trial (1945).

[1] It has been argued by some, such as poet Lars Gustafsson[2] and politician Per Ahlmark,[3] that Vennberg expressed support for fascism and nazism.

However, these accusations were later revealed to be based largely on quotes taken out of context, and the truth is that Vennberg actually held strong anti-fascist views; for example, in his diary in 1935, he described nazism as "nothing but private capitalism's last resort".

Vennberg was also a member of the Swedish Clarté League, a socialist students' organization which resolutely opposed fascism and nazism in the 1930s and 1940s.

[5] Karl Vennberg won a number of literary prizes during his career: He was also awarded an honorary doctorate at Stockholm University.