The Italian beat the 12th seed 6-7 6-3 2-6 6-4 6-4 earlier today to equal his best ever performance in a Grand Slam tournament.
The 28-year-old said: "It's the first time I've passed the second round here also in Australia, so it is very important for me. One of my goals was to go better in the slams."
Seppi also made the fourth round of the French Open last year.
The 21st seed will face Jeremy Chardy in the next round.