The 33-year-old all-rounder will fill the first of two overseas player positions throughout the competition, which is set to take place predominantly in July and August.
Among the former Australian international’s three T20 half-centuries last summer was the 16-ball cameo against Leicestershire Foxes that equalled Alex Hales’ record for the Outlaws’ fastest fifty in T20 cricket.
“Dan is an explosive player who hits the ball miles and played really well for us last year,” said Nottinghamshire Head Coach Peter Moores.
“He’s also been around the T20 scene and around cricket for a long time. He brings all that experience to us, as well as a real calmness under pressure.”
Christian’s white ball record includes 34 appearances for his country, 11 successive campaigns in the Big Bash and two seasons with the Deccan Chargers in the Indian Premier League.
His T20 career spans 174 appearances, 2,549 runs at a batting index of 154.5 and 130 wickets at 29.92 apiece.
“Anybody who has met Dan will know he’s a brilliant team man,” added Moores.
“He’s a great character to have around and that competitive nature that you find in a lot of Australians is certainly in him.
“He gives everything and expects the same from his teammates. He likes to get on the front foot, to be aggressive and to play attacking cricket, which is exactly what we want in that form of the game.”