Like his father, James Jr. was an active abolitionist; In fact, James Jr. had already been a writer for the abolitionist publication the Liberator by the time he was a teenager.

He was also a member of several abolitionist organizations including the American Moral Reform Society, and the Young Men's Anti-Slavery Society.

On April 14, 1836, a 19 year old James forten Jr. delivered a long and powerful address to the Female Anti-slavery Society encouraging these women to continue their fight for abolition, ending his address by stating “God is with you…and in the darkest and most perilous hour of your enterprise, your fortitude will not forsake you; and, remembering under what influences you have reared the Banner of Universal Freedom, your enemies will be constrained to admit that no power on earth can ever oppose the Arm of Omnipotence.”

James fathered a son named James Vogelsang Forten.