Djokovic, who has been dealing with an abdominal injury in Melbourne, brushed past qualifier Karatsev 6-3 6-4 6-2 in their semi-final on Rod Laver Arena.
The world number one has won the Australian Open every time he has reached the semi-finals, and he is on track again ahead of facing either Daniil Medvedev or Stefanos Tsitsipas in Sunday's decider.
Djokovic moved into his 28th grand slam final – a tally bettered only by Roger Federer (31) – as he targets an 18th major title.
Karatsev held his own in the early baseline exchanges and dug himself out of a 0-30 hole in the sixth game.
But he could not deny Djokovic in his next service game, broken to love when he pulled a backhand wide as the Serbian won 10 straight points and the set.
Djokovic broke again in the third game of the second set following a Karatsev double fault, and a fortunate net cord saw him into a 4-1 lead as he took complete control.
Karatsev got one of the breaks back and pushed for the other, but Djokovic – who had won all 19 of his previous meetings with qualifiers at grand slams – closed out the second set.
Just as Karatsev seemed to be working his way back into the contest and the duo exchanged breaks to begin the third, Djokovic took a 3-2 lead as he won the final four games of the match.