The Greek world No.7 saw off a stern test from Elise Mertens on Saturday (AEDT), winning 7-6 (9-7) 6-2 to reach the semi-finals.
Sakkari had to salvage three set points in the opener, but eventually came out on top in the tie-break at the first time of asking.
Even with a comfortable lead in the second set, she failed to take the first three match points on offer, but got the fourth over the line to progress to her first semi-final of the season.
Sakkari, 26, previously reached the St Petersburg semi-final in 2020, where she lost to Elena Rybakina.
"When you're down in the score, you try to play more aggressively and [Elise] was playing really good in the last couple of games," Sakkari explained.
"She came up with good serves and solid shots from the baseline. I just fought hard."
Irina-Camelia Begu stands in the way of Sakkari and a place in the final.
