The top-seeded Greek saved three straight set points in the tiebreaker fighting off Grigor Dimitrov 7-6(6), 6-4 to reach the Vienna second round.
Tsitsipas avenged a three-set loss to Dimitrov in Vienna last year setting up a round-of-16 clash vs. American Frances Tiafoe, who topped Dusan Lajovic 6-4, 6-4.
French Open finalist Tsitsipas flipped the script on Dimitrov with a determined tiebreaker and dynamic second-set raising his 2021 record to an ATP-best 55-16.
"We both competed at our highest [level]. That was great tennis that was being played during the entire match and I got really close to my [best] offence and showed incredible attitude [in] the last game, which was the one that was the most crucial of the match." said Tsitsipas after the match"