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Mundine, coming off a heavy loss to Joshua Clottey in April, racked up the points in the first four rounds against a slow and uncertain Rabchenko.
After a sluggish start the previously undefeated Belarusian worked his way back into the contest in the middle rounds to draw level on the official scorecards after eight.
One judge had it 77-75 to Rabchenko, another for Mundine 77-75 and the third scored it 77-77 with four rounds remaining.
The Belarusian hurt Mundine badly with a vicious body shot late in the 10th round and followed up with a flurry of punches that Mundine somehow survived.
Mundine also wore a vicious right hand at the end of the 11th but did enough in the eyes of two of the three judges to win the WBC silver light middleweight title with a split points decision.
One judge scored the bout 115-113 to Rabchenko, while the other two ruled in favour of the Australian 115-113 and 116-112.
With the win Mundine improves to a 47-6 professional record while Rabchenko drops to 25-1.
Mundine is now the mandatory challenger for Floyd Mayweather's WBC light middleweight title.
"I think Floyd, he's the best of our era and I'm not going to disrespect him," Mundine said.
"It's up to him if he wants to fight me, if he doesn't hopefully we can fight someone like (Saul) Alvarez," Mundine said.
"I fought his brother so there's history there and I think it's a great match-up stylistically.
"That was a hard fight for my stylistically but Alvarez is more of a counter-puncher and it'd be a better fight for me."
Mundine praised Rabchenko after the fight but couldn't resist taking a swipe at those who dared to doubt him.
"You all thought I was done, but I'm not done until I say I'm done," he said.
"I've got a few more, make a few mill and then I'm out.
"I fought a young lion tonight, a young lion that can punch.
"He's got power in both hands, got good body rips but I took everything he had, I showed my chin plus my heart and I know I rocked him too a few times."