When Charles Hardenbergh died in 1806, nine-year-old Truth (known as Belle), was sold at an auction with a flock of sheep for $100 to John Neely, near Kingston, New York. Until that time, Truth spoke only Dutch. She later described Neely as cruel and harsh, relating how he beat her daily and once even with a bundle of rods. Neely sold her in 1808, for $105, to Martinus Schryver of Port Ewen, a tavern keeper, who owned her for eighteen months. Schryver sold her in 1810 to John Dumont of West Park, New York. Although this fourth owner was kindly disposed toward her, considerable tension existed between Truth and Dumont's second wife, Elizabeth Waring Dumont, who harassed her and made her life more difficult. (John Dumont's first wife, Sarah "Sally" Waring Dumont (Elizabeth's sister), died around 1805, five years before he bought Truth.)

Around 1815, Truth met and fell in love with a slave named Robert from a neighboring farm. Robert's owner (Charles Catton, Jr., a landscape painter) forbade their relationship; he did not want the people he enslaved to have children with people he was not enslaving, because he would not own the children. One day Robert sneaked over to see Truth. When Catton and his son found him, they savagely beat Robert until Dumont finally intervened, and Truth never saw Robert again. He died some years later, perhaps as a result of the injuries, and the experience haunted Truth throughout her life. Truth eventually married an older slave named Thomas. She bore five children: James, her firstborn, who died in childhood, Diana (1815), fathered by either Robert or John Dumont, and Peter (1821), Elizabeth (1825), and Sophia (ca. 1826), all born after she and Thomas united.

Late in 1826, Truth escaped to freedom with her infant daughter, Sophia. She had to leave her other children behind because they were not legally freed in the emancipation order until they had served as bound servants into their twenties. She later said "I did not run off, for I thought that wicked, but I walked off, believing that to be all right."

The state of New York began, in 1799, to legislate the abolition of slavery, although the process of emancipating those people enslaved in New York was not complete until July 4, 1827. Dumont had promised to grant Truth her freedom a year before the state emancipation, "if she would do well and be faithful." However, he changed his mind, claiming a hand injury had made her less productive. She was infuriated but continued working, spinning 100 pounds of wool, to satisfy her sense of obligation to him.

Truth learned that her son Peter, then five years old, had been sold illegally by Dumont to an owner in Alabama. With the help of the Van Wagenens, she took the issue to court and in 1828, after months of legal proceedings, she got back her son, who had been abused by those who were enslaving him. Truth became one of the first black women to go to court against a white man and win the case.

Truth had a life-changing religious experience during her stay with the Van Wagenens, and became a devout Christian. In 1829 she moved with her son Peter to New York City, where she worked as a housekeeper for Elijah Pierson, a Christian Evangelist. While in New York, she befriended Mary Simpson, a grocer on John Street who claimed she had once been enslaved by George Washington. They shared an interest in charity for the poor and became intimate friends. In 1832, she met Robert Matthews, also known as Prophet Matthias, and went to work for him as a housekeeper at the Matthias Kingdom communal colony. Elijah Pierson died, and Robert Matthews and Truth were accused of stealing from and poisoning him. Both were acquitted of the murder, though Matthews was convicted of lesser crimes, served time, and moved west.

In 1839, Truth's son Peter took a job on a whaling ship called the Zone of Nantucket. From 1840 to 1841, she received three letters from him, though in his third letter he told her he had sent five. Peter said he also never received any of her letters. When the ship returned to port in 1842, Peter was not on board and Truth never heard from him again.

1843 was a turning point for Truth. She became a Methodist, and on June 1, she changed her name to Sojourner Truth. She told friends: "The Spirit calls me, and I must go" and left to make her way traveling and preaching about the abolition of slavery. At that time, Truth began attending Millerite Adventist campmeetings. However, that did not last since Jesus failed to appear in 1843 and then again in 1844. Like many others disappointed, Truth distanced herself from her Millerite friends for a while.

In 1844, she joined the Northampton Association of Education and Industry in Northampton, Massachusetts. Founded by abolitionists, the organization supported women's rights and religious tolerance as well as pacifism. There were, in its four-and-a-half year history, a total of 240 members, though no more than 120 at any one time. They lived on 470 acres (1.9 km), raising livestock, running a sawmill, a gristmill, and a silk factory. While there, Truth met william Lloyd Garrison, Frederick Douglass, and David Ruggles. In 1846, the group disbanded, unable to support itself. In 1845, she joined the household of George Benson, the brother-in-law of william Lloyd Garrison. In 1849, she visited John Dumont before he moved west.

Truth started dictating her memoirs to her friend Olive Gilbert, and in 1850 william Lloyd Garrison privately published her book, The Narrative of Sojourner Truth: A Northern Slave. That same year, she purchased a home in what would become the village of Florence in Northampton for $300, and spoke at the first National Women's Rights Convention in Worcester, Massachusetts. In 1854, with proceeds from sales of the Narrative and cartes-de-visite entitled "I sell the Shadow to support the substance," she paid off the mortgage held by her friend from the Community, Samuel L. Hill.

Over the next 10 years, Truth spoke before dozens, perhaps hundreds, of audiences. From 1851 to 1853, Truth worked with Marius Robinson, the Editor of the Ohio Anti-Slavery Bugle, and traveled around that state speaking. In 1853, she spoke at a suffragist "mob convention" at the Broadway Tabernacle in New York City; that year she also met Harriet Beecher Stowe. In 1856, she traveled to Battle Creek, Michigan, to speak to a group called the "Friends of Human Progress." In 1858, someone interrupted a speech and accused her of being a man; Truth opened her blouse and revealed her breasts.

Mob Convention—September 7, 1853: At the convention, young men greeted her with "a perfect storm,” hissing and groaning. In response, Truth said, "You may hiss as much as you please, but women will get their rights anyway. You can't stop us, neither". Sojourner, like other public speakers, often adapted her speeches to how the audience was responding to her. In her speech, Sojourner speaks out for women's rights. She incorporates religious references in her speech, particularly the story of Esther. She then goes on to say that, just as women in scripture, women today are fighting for their rights. Moreover, Sojourner scolds the crowd for all their hissing and rude behavior, reminding them that God says to "Honor thy Father and thy mother."

In 1856, Truth bought a neighboring lot in Northampton, but she did not keep the new property for long. On September 3, 1857, she sold all her possessions, new and old, to Daniel Ives and moved to Battle Creek, Michigan, where she rejoined former members of the Millerite Movement who had formed the Seventh-day Adventist Church. Antislavery movements had begun early in Michigan and Ohio. Here, she also joined the nucleus of the Michigan abolitionists, the Progressive Friends, some who she had already met at national conventions. According to the 1860 census, her household in Harmonia included her daughter, Elizabeth Banks (age 35), and her grandsons James Caldwell (misspelled as "Colvin"; age 16) and Sammy Banks (age 8).

According to Frances Gage's recount in 1863, Truth argued, "That man over there says that women need to be helped into carriages, and lifted over ditches, and to have the best place everywhere. Nobody helps me any best place. And ain't I a woman?" Truth's " Ain't I a Woman" showed the lack of recognition that Black women received during this time and whose lack of recognition will continue to be seen long after her time. " Black women, of course, were virtually invisible within the protracted campaign for woman suffrage" as said by Davis supports Truth's argument that nobody gives her " any best place" but not only her but Black women in general.

During the Civil War, Truth helped recruit black troops for the Union Army. Her grandson, James Caldwell, enlisted in the 54th Massachusetts Regiment. In 1864, Truth was employed by the National Freedman's Relief Association in Washington, D.C., where she worked diligently to improve conditions for African-Americans. In October of that year, she met President Abraham Lincoln. In 1865, while working at the Freedman's Hospital in Washington, Truth rode in the streetcars to help force their desegregation.

In 1867, Truth moved from Harmonia to Battle Creek. In 1868, she traveled to western New York and visited with Amy Post, and continued traveling all over the East Coast. At a speaking engagement in Florence, Massachusetts, after she had just returned from a very tiring trip, when Truth was called upon to speak she stood up and said "Children, I have come here like the rest of you, to hear what I have to say."

In 1870, Truth tried to secure land grants from the federal government to former enslaved people, a project she pursued for seven years without success. While in Washington, D.C., she had a meeting with President Ulysses S. Grant in the White House. In 1872, she returned to Battle Creek and tried to vote in the presidential election, but was turned away at the polling place.

Several days before Sojourner Truth died, a reporter came from the Grand Rapids Eagle to interview her. "Her face was drawn and emaciated and she was apparently suffering great pain. Her eyes were very bright and mind alert although it was difficult for her to talk." Truth died at her Battle Creek home on November 26, 1883. On November 28 her funeral was held at the Congregational-Presbyterian Church officiated by its pastor, the Reverend Reed Stuart. Some of the prominent citizens of Battle Creek acted as pall-bearers. Truth was buried in the city's Oak Hill Cemetery.

A larger-than-life sculpture of Sojourner Truth by Artist Tina Allen, was dedicated in 1999, which is the estimated bicentennial of Sojourner's birth. The 12-foot tall Sojourner monument is cast bronze.

Eighth Anniversary of Negro Freedom—New Year's Day, 1871: On this occasion the Boston papers related that “...seldom is there an occasion of more attraction or greater general interest. Every available space of sitting and standing room was crowded". She starts off her speech by giving a little background about her own life. Sojourner recounts how her mother told her to pray to God that she may have good masters and mistresses. She goes on to retell how her masters were not good to her, about how she was whipped for not understanding English, and how she would question God why he had not made her masters be good to her. Sojourner admits to the audience that she had once hated white people, but she says once she met her final master, Jesus, she was filled with love for everyone. Once enslaved folks were emancipated, she tells the crowd she knew her prayers had been answered. That last part of Sojourner's speech brings in her main focus. Some freed enslaved people were living on government aid at that time, paid for by taxpayers. Sojourner announces that this is not any better for those colored people than it is for the members of her audience. She then proposes that black people are given their own land. Because a portion of the South's population contained rebels that were unhappy with the abolishment of slavery, that region of the United States was not well suited for colored people. She goes on to suggest that colored people be given land out west to build homes and prosper on.

As of March 2015, K-12 schools in several states, including California, Minnesota, New Jersey, New York and Oregon, are named after her, as is Sojourner–Douglass College in Baltimore.

The U.S. Treasury Department announced in 2016 that an image of Sojourner Truth will appear on the back of a newly designed $10 bill along with Lucretia Mott, Susan B. Anthony, Elizabeth Cady Stanton, Alice Paul and the 1913 Woman Suffrage Procession. Designs for new $5, $10 and $20 bills will be unveiled in 2020 in conjunction with the 100th anniversary of American women winning the right to vote via the Nineteenth Amendment to the United States Constitution.