The UFC announced Thursday that the two will meet Oct. 4 in the main event of a televised UFC card at the Halifax Metro Centre.
MacDonald, a native of Kelowna, B.C., now fighting out of Montreal, is ranked No. 2 among UFC 170-pound contenders. Saffiedine, a Belgian based out of the U.S., is ranked 10th.
The 25-year-old MacDonald has won seven of his last eight bouts and is 8-2 in the UFC since making his debut in the organization in January 2010. His lone UFC losses have come at the hands of (Ruthless) Robbie Lawler, at UFC 167 last November, and Carlos (The Natural Born Killer) Condit, at UFC 115 in June 2010.
Lawler went on to lose a decision to Johny (Bigg Rigg) Hendricks to decide who would take over the title vacated by Georges St-Pierre, who trains with MacDonald. Hendricks won by decision, with Lawler earning another title shot after disposing of Matt (The Immortal) Brown on the weekend.
The six-foot MacDonald is coming off an impressive win over No. 4 Tyron Woodley at UFC 174 in June in Vancouver following a decision over jiu-jitsu ace Demian Maia at UFC 170 in February.
MacDonald (17-2) is a rangy well-rounded fighter who can do damage from the outside with an effective jab. But he is also dangerous in close, able to slam opponents and punish them on the ground.
The Canadian will have a six-inch advantage in reach and two inches in height on Saffiedine.
Saffiedine (13-3) has won five straight since dropping a decision to Woodley in Strikeforce in January 2011. His last outing, which was his UFC debut, was a decision win over Hyun Gyu Lim in January.
The 27-year-old Belgian, who won eight of his last nine fights, is a former kick-boxer with a black belt in karate and a brown belt in Brazilian jiu-jitsu. MacDonald is a black belt in BJJ.
A win over Saffiedine would be MacDonald's fourth over a top-10 welterweight fighter.
The Halifax show marks the UFC's first in Nova Scotia.