Sara Cohen was born on May 1, 1980, in New York City and grew up in midtown Manhattan. Her father was a psychiatrist, and her mother was a podiatrist; they later divorced. She has one younger brother. From an early age, she expressed an interest in becoming a physician. She attended a highly competitive New York City high school, later suggesting that the academic rigor she experienced there was formative to her work ethic.
Cohen went on to study mathematics at Harvard University. Later, she attended medical school at Stony Brook University, pursuing a career in medicine, while continuing to write fiction and submit manuscripts to publishers and literary agents.
