Jacobs, 25 was born in Johannesburg, but has spent his entire career in Scotland with Livingston FC.
He is the son of Davy Jacobs, who scored the winner for Wits University against Kaizer Chiefs in the 1978 Mainstay Cup final.
“He will offer a lot, he is very much like his dad,”said Wits coach Gavin Hunt on Friday.
“He has played overseas since he was a kid, he has come back here and done very well, he has the right attitude.
“For me he is a good midfield player, though it will take him time to settle down to the way football is played here.”
— Keaghan Jacobs (@keagsojac7) July 10, 2015
Meanwhile, Wits also announced the signing of New Zealand striker Kris Bright and Malawian midfielder Gerald Phiri Jnr.