Born in Uniontown, Pennsylvania, he was grandson of Joshua Seney, and was also descended from colonial Governor of Maryland Francis Nicholson. Seney moved to Tiffin, Ohio with his parents in 1832. He attended Norwalk Seminary, studied law and was admitted to the bar in 1853, commencing practice in Tiffin. He declined appointment as United States Attorney for the Northern District of Ohio, tendered by President James Buchanan. He was a judge of the court of common pleas in 1857 and during the Civil War, enlisted in the 101st Ohio Infantry in 1862 where he was promoted to first lieutenant and later acted as quartermaster of the regiment until the close of the war. He lost election to the United States House of Representatives in 1874 by less than 140 votes. Seney was a delegate to the Democr