Joseph Simon Cohen was one of eight children born to Solomon Myers-Cohen, a New York merchant, and Belle Simon Cohen, daughter of Joseph Simon, a Lancaster, Pennsylvania, trader. Solomon and Belle were involved with Congregation Shearith Israel in New York, but when the British occupied the city in 1776, they fled with their young family to Philadelphia. There Solomon served with the Third Battalion of the Pennsylvania Militia. Although the family returned to New York quickly after the war, with Solomon’s death, in 1796, they again moved to Philadelphia, where Belle and her children would become prominent figures in the community around Congregation Mikveh Israel.

Joseph graduated from the University of Pennsylvania and was admitted to the bar in 1813. From 1840 to 1853 he was prothonotary of the Supreme Court of Pennsylvania. He remained active with Mikveh Israel and gave a sermon to the congregation on the day of Thanksgiving to mark the end of the War of 1812. He never married and seems not to have had children.