Nancy became a writer and in 1931 published her first novel, Highland Fling. This was followed by Christmas Pudding (1932). The following year she married Peter Rodd.
Nancy's parents held right-wing political views and supported the British Union of Fascists and their daughter, Diana Mitford, married its leader, Oswald Mosley. Another sister, Unity Mitford went to Nazi Germany and met Adolf Hitler, Heinrich Himmler, Herman Goering, Joseph Goebbels and other leaders of the Nazi Party.
Nancy, like her sister, Jessica Mitford, was a socialist and in 1935 published Wigs on the Green, a satirical novel about her sisters involvement with the British Union of Fascists. This was followed by Pigeon Pie (1940).
After the Second World War Mitford achieved commercial success with the novels The Pursuit of Love (1945) and Love in a Cold Climate (1949). Other novels by Mitford included The Blessing (1951) and Don't Tell Alfred (1960).
Nancy Mitford died in 1973.