Anna Lea Merritt was born in Philadelphia on September 13, 1844, the daughter of Joseph Lea, a manufacturer. As women were generally excluded from art academies at the time, she instead practiced art on her own, and later studied anatomy at the Woman's Medical College of Pennsylvania. She further studied art in Italy, Germany, and Paris. In 1865, when Merritt was in her early twenties, her father moved the family to Europe where her art was critiqued by Stefano Ussi and Heinrich Hoffman. When she was living in London in 1870, Meritt met Henry Merritt, who would become her tutor and later, her husband. Merrit was an artist, and critic, who was twenty two years her senior. Tragically he died three months after the wedding. Anna Merritt edited a selection of her husband’s writings for publication.

She built up a thriving practice as a portrait painter, in which artistic sphere she was highly talented - her picture of two little sisters, Jacqueline and Isura Loraine, for example is highly accomplished. Merritt painted her best-known work, Love Locked Out, in memory of her late husband, who died in 1877 just three months after their wedding. She had hoped to have the image done in bronze as a monument, but could not afford it. Merritt initially resisted allowing the painting to be copied despite innumerable” requests, because she feared the subject would be misinterpreted: “I feared people liked it as a symbol of forbidden love,” she wrote in her memoir, “while my Love was waiting for the door of death to open and the reunion of the lonely pair”. Love Locked Out was exhibited at the Royal Academy in 1890 and became the first painting by a woman artist acquired for the British national collection through the Chantrey Bequest.

In 1900, Merritt wrote that she felt she had not faced much if any discrimination because of her gender, but noted the social pressures which could inhibit a female artist's career, concluding:

“The chief obstacle to a woman's success is that she can never have a wife. Just reflect what a wife does for an artist: Darns the stockings; keeps his house; writes his letters; visits for his benefit; wards off intruders; is personally suggestive of beautiful pictures; always an encouraging and partial critic. It is exceedingly difficult to be an artist without this time-saving help. A husband would be quite useless."

Anna Lea Merritt died on April 7, 1930 in Hurstborne Tarrant, Hampshire, England.