After college, Jacoby was snubbed in the NFL draft. He signed a free agent contract with the Redskins in 1981. After clawing his way through rookie camp, he embarked on an enviable career—four Super Bowl appearances, of which his team won three (XVII in 1983, XXII in 1988, and XXVI in 1992), plus four consecutive Pro Bowl selections from 1983–86.
Along with Jeff Bostic, Mark May, George Starke and Russ Grimm, Jacoby was a founding member of the Redskins' renowned "Hogs" offensive line of the 1980s and early 1990s (deemed one of the best front fives of NFL history), which was a mainstay of the Redskins' glory years during the first Joe Gibbs era.
Jacoby was the lead blocker on John Riggins' famous touchdown run which ensured the Redskins' Super Bowl XVII win over the Dolphins in 1983. In that game, the Redskins set a Super Bowl record for most rushing yards with 276. The Hogs helped the Redskins break that record five years later in Super Bowl XXII, in which Washington trampled over the Denver Broncos with 280 rushing yards en route to the second of the Redskins' three championships.
One year after the Redskins' third Super Bowl victory in 1992, Jacoby hung up his cleats and retired, after which he became the owner of an auto dealership in Warrenton, Virginia. He no longer owns the dealership as of February, 2008.