According to her husband, Plath began writing the novel in 1961, after publishing The Colossus, her first collection of poetry. Plath finished writing the novel in August 1961. After she separated from Hughes, Plath moved to a smaller flat in London, "giving her time and place to work uninterruptedly. Then at top speed and with very little revision from start to finish she wrote The Bell Jar," he explained.
Plath was writing the novel under the sponsorship of the Eugene F. Saxton Fellowship, affiliated with publisher Harper & Row, but it was disappointed by the manuscript and withdrew, calling it "disappointing, juvenile and overwrought." Early working titles of the novel included Diary of a Suicide and The Girl in the Mirror.