She married James T. Fields on November 15, 1854, in King's Chapel in Boston with a service conducted by Reverend Ezra Stiles Gannett. She was his second wife; his first was a cousin of hers. Her husband was a well-established and respected publisher and with him she encouraged up and coming writers such as Sarah Orne Jewett, Mary Eleanor Wilkins Freeman, and Emma Lazarus. She was equally at home with great and established figures including Ralph Waldo Emerson and Harriet Beecher Stowe, whose biography she compiled. At their home at 148 Charles Street in Boston, she established a regular literary salon where authors gathered. Fields was also a philanthropist and social reformer; in particular, she founded the Holly Tree Inns, coffeehouses serving inexpensive and nutritious meals, and the Lincoln Street Home, a safe and inexpensive residence for unmarried working women.