After Johnson's death in 1774, Brant and her children left Johnson Hall in Johnstown, New York and returned to her native village of Canajoharie, further west on the Mohawk River. A Loyalist during the American Revolutionary War, she migrated to British Canada, where she served as an intermediary between British officials and the Iroquois. After the war, she settled in what is now Kingston, Ontario. In recognition of her service to the Crown, the British government gave Brant a pension and compensated her for her wartime losses, including a grant of land. When the British ceded their former colonial territory to the United States, most of the Iroquois nations were forced out of New York. A Six Nations Reserve was established in what is now Ontario.
Since 1994, Brant has been honored as a Person of National Historic Significance in Canada. She was long ignored or disparaged by historians of the United States, but scholarly interest in her increased in the late 20th century. She has sometimes been controversial, criticized for being pro-British at the expense of the Iroquois. But the Iroquois primarily allied with the British. Known to have been a devout Anglican, she is commemorated on April 16 in the calendar of the Anglican Church of Canada and the Episcopal Church (USA). No portraits of her are known to exist; an idealized likeness is featured on a statue in Kingston and on a Canadian stamp issued in 1986.
Little is known for certain about Molly Brant's early life. Named Mary, but commonly known as "Molly", she was born around 1736, possibly in the Mohawk village of Canajoharie, or perhaps further west in the Ohio Country. Her parents were Christian Mohawks. French Jesuit missionaries had converted many Mohawk to Catholicism in their early colonial years. By the mid-18th century, however, English influence had grown in New York. Christian Mohawk tended to realign as Anglicans. Brant may have been the child named Mary who was christened at the chapel at Fort Hunter, near the Lower Castle, another Mohawk village, on April 13, 1735. If so, her parents were named Margaret and Cannassware. Most historians believe that her father was named Peter. Joseph Brant, born in 1743, was Molly's brother or half-brother.
One of Molly's Mohawk names, perhaps her birth name, was Konwatsi'tsiaienni, which means "Someone Lends Her a Flower". Her other Mohawk name, given to her at adulthood in a customary mark of passage, was Degonwadonti, meaning "Two Against One". Her Mohawk names have been spelled in a variety of ways in historical records.
The Mohawk are one of the Six Nations of the Iroquois League and occupied the most eastern territory of the confederacy. At the time of the American Revolutionary War, they lived primarily in the Mohawk River valley in what is now upstate New York, west of what developed as colonial Albany and Schenectady. At some point, either before or after her birth, Molly's family moved west to the Ohio Country, which the Iroquois had reserved as a hunting ground since the late 17th century.