Welch was born in Glastonbury, England on December 31, 1825. He moved to the United States when his father emigrated in 1834. He attended public schools in Watertown, New York.

Welch then relocated to Winona, Minnesota in 1856. He changed his profession to dentistry.

In 1864, the General Conference of the Methodist Episcopal Church expressly recommended that “in all cases the pure juice of the grape be used in the celebration of the Lord’s Supper.” In 1865, Welch relocated to Vineland, New Jersey, where a sister already resided, and became a member of Vineland Methodist Episcopal Church, where he served as a communion steward. Then in 1869, Welch invented a method of pasteurizing grape juice so that fermentation was stopped, and the drink was non-alcoholic. He persuaded local churches to adopt this non-alcoholic wine for communion services, calling it “Dr. Welch’s Unfermented Wine.”

His son, Charles E. Welch, also a dentist, returned to Vineland, New Jersey, in 1875 and later relocated his dental practice to Vineland. By this time his father was a successful Prohibition crusader, and had “all but abandoned” attention to his old experiments. He advised Charles, “Now don’t think I’m trying to discourage your pushing the grape juice. It is right for you to do so, so far as you can, without interfering with your profession and your health.” Charles and Thomas Welch founded the Welch’s Dental Supply Company in Philadelphia and began a dentistry journal. Charles promoted the sale and consumption of grape juice. The Welches sold grape juice as a sideline. The industry had grown slowly until 1890. So from 1890, the Welches were able to spend more attention on the industry. Charles did not devote full attention to marketing grape juice until 1893, when Welch’s Grape Juice Company was “officially launched”. However, Thomas Welch himself “never received a penny in return for his investment.”

After the death of his first wife, Thomas Welch married Miss Victoria C. Sherbume in 1895.

On December 29, 1903, Thomas Welch died at Vineland and is buried in its Siloam Cemetery.