Hardenbergh studied theological under the Reverend John Frelinghuysen, a Reformed clergyman who served several congregations located in the valley of the Raritan River in Somerset County, New Jersey, at the village of Raritan, Bedminster, Millstone, Neshanic, North Branch, and New Brunswick.
 These congregations had been served by Frelinghuysen's father, the Reverend Theodorus Jacobus Frelinghuysen (1691–1749), who rose to prominence during the First Great Awakening.
 The First Great Awakening was an evangelical revival in the 1730s and 1740s that revitalized Christian beliefs in Protestant Europe and the North American colonies through powerful preaching that gave listeners a sense of deep personal revelation of their need of salvation by Jesus Christ.
Frelinghuysen had adapted the theological developments of the Puritan divines to preach a style of Reformed pietism, a revivalistic style of Calvinism.
 His son, John, preached and instructed his students in the same style.

With John Frelinghuysen's unexpected death in 1754, Hardenbergh, as his last theological student, assumed the pulpits of five congregations in central New Jersey served by his teacher.
In 1757, Hardenbergh received a license to preach from the Coetus and was formally called by these congregations in May 1758.
In 1761, the Coetus relieved him of two of these congregations, at Millstone and New Brunswick.

During the Revolution, General Washington, a personal friend of the Hardenbergh family, established a headquarters at Raritan in the home of John Wallace and frequently attended services sitting "at the head of the elder's pew".
In 1779, the church at Raritan was burned by British forces under Colonel John Graves Simcoe who had intensified efforts to capture Washington.
The church was not rebuilt until 1788.

In 1781, Hardenbergh resigned his pastorates in New Jersey to accept the call to congregations at Marbletown, Rochester, and Wawarsing in Ulster County, New York.
 He would serve these congregations until 1785.
In October 1785, Hardenbergh was called to serve as pastor to the congregation at the First Reformed Church in New Brunswick, New Jersey.
He would arrive in New Brunswick to assume the pastorate in April 1786.
At the same time, the trustees of Queen's College had called Hardenbergh, a devoted trustee for the school, to serve as its first appointed president.
 Hardenbergh was invited to fill a vacancy left by the death of the Rev. Johannes Leydt (1719–1783).
For two years the church had been served by neighboring clergymen.
Hardenbergh had trained both of Leydt's sons in theology—Matthew Leydt (who also died in 1783) was the first graduate of Queen's College.
He would serve the congregation until his sudden death in 1790.
 According to church historian, Richard Holloway Steele, Hardenbergh was the last pastor at New Brunswick to preach in Dutch.

On four occasions, Hardenbergh was selected to serve as the President of the General Synod of the Dutch Reformed Church.
Hardenbergh studied theological under the Reverend John Frelinghuysen, a Reformed clergyman who served several congregations located in the valley of the Raritan River in Somerset County, New Jersey, at the village of Raritan, Bedminster, Millstone, Neshanic, North Branch, and New Brunswick.  These congregations had been served by Frelinghuysen's father, the Reverend Theodorus Jacobus Frelinghuysen (1691–1749), who rose to prominence during the First Great Awakening.  The First Great Awakening was an evangelical revival in the 1730s and 1740s that revitalized Christian beliefs in Protestant Europe and the North American colonies through powerful preaching that gave listeners a sense of deep personal revelation of their need of salvation by Jesus Christ. Frelinghuysen had adapted the theological developments of the Puritan divines to preach a style of Reformed pietism, a revivalistic style of Calvinism.  His son, John, preached and instructed his students in the same style.
With John Frelinghuysen's unexpected death in 1754, Hardenbergh, as his last theological student, assumed the pulpits of five congregations in central New Jersey served by his teacher. In 1757, Hardenbergh received a license to preach from the Coetus and was formally called by these congregations in May 1758. In 1761, the Coetus relieved him of two of these congregations, at Millstone and New Brunswick.
During the Revolution, General Washington, a personal friend of the Hardenbergh family, established a headquarters at Raritan in the home of John Wallace and frequently attended services sitting "at the head of the elder's pew". In 1779, the church at Raritan was burned by British forces under Colonel John Graves Simcoe who had intensified efforts to capture Washington. The church was not rebuilt until 1788.
In 1781, Hardenbergh resigned his pastorates in New Jersey to accept the call to congregations at Marbletown, Rochester, and Wawarsing in Ulster County, New York.  He would serve these congregations until 1785. In October 1785, Hardenbergh was called to serve as pastor to the congregation at the First Reformed Church in New Brunswick, New Jersey. He would arrive in New Brunswick to assume the pastorate in April 1786. At the same time, the trustees of Queen's College had called Hardenbergh, a devoted trustee for the school, to serve as its first appointed president.  Hardenbergh was invited to fill a vacancy left by the death of the Rev. Johannes Leydt (1719–1783). For two years the church had been served by neighboring clergymen. Hardenbergh had trained both of Leydt's sons in theology—Matthew Leydt (who also died in 1783) was the first graduate of Queen's College. He would serve the congregation until his sudden death in 1790.  According to church historian, Richard Holloway Steele, Hardenbergh was the last pastor at New Brunswick to preach in Dutch.
On four occasions, Hardenbergh was selected to serve as the President of the General Synod of the Dutch Reformed Church.
Jacob Rutsen Hardenbergh