In 1937 Janečková won the Czech Women's Chess Championship. In 1938 she finished second in the Czechoslovak Women's Chess Championship. In 1939 she participated in the Women's World Chess Championship in Buenos Aires and tied for 9–10th place (tournament won by Vera Menchik). After returning to her homeland from the Women's World Championship in Argentina, Janečková won the Women's Chess Championship in Bohemia and Moravia in 1940. In early 1941 Janečková was arrested by the Gestapo because she was a member by Communist Party of Czechoslovakia and worked in the Czech intelligence resistance group founded by Julius Fučík. She spent four years in the concentration camp.