After school training he was educated for the presbyterian ministry by Timothy Jollie, at Attercliffe Academy, Yorkshire.
In 1709 he was chosen assistant preacher to one of the foremost presbyterian congregations in London, at Crosby Square.
On the death of Matthew Henry the commentator in June 1714, his congregation in Mare Street, Hackney, London, invited Barker to succeed him.
Shortly after his settlement at Hackney, Barker took part in the historic controversies on the Trinity, which divided Protestant dissenters into two hostile camps, respectively known as subscribers and non-subscribers.
Barker belonged to the former, and delivered a series of discourses on the supreme and absolute divinity of Jesus Christ.
Prefixed to what Tomkins called 'A Calm Inquiry whether we have any Warrant from Scripture for addressing ourselves in a Way of Prayer or Praise to the Holy Spirit,' is 'A Letter to the Rev.
After his resignation at Hackney, he retired to Epsom in Surrey, where he lived for about three years without any charge, but was always ready to assist his brethren.
Secondly he married the widow of a Mr. Lamb, whose large house in Hackney (London Fields) gave name to 'Lamb's Lane.'