World No.16 Sevastova looked set to make short work of Sasnovich after losing the least amount of games (13) of all the semi-finalists and was yet to drop a set this week.
Sasnovich had come from a set down to win her first three main-draw matches, but had no answer to Svitolina's power after falling behind on this occasion.
"It was a tough, tough offseason", Svitolina said, on court after the match.
Svitolina said: "It was a tough offseason". It was a good week for me'.
Svitolina won in just 65 minutes.
In the tiebreak, Sasnovich got off to a quick start, earning the first mini-break with another backhand victor for a 2-0 lead.
A flurry of brutal groundstrokes brought up a pair of set points for Svitolina, who delivered at the second time of asking, sealing the first set 6-2.
World No.88 Sasnovich of Belarus - ranked 72 spots lower than her opponent - called for a medical timeout after the first set to have new strapping applied to quell a leg complaint that has troubled her throughout the tournament.
In doing so, she will raise her ranking into the top 60, but that counted for little.
She will play Elina Svitolina for the title. Sasnovich did not have a single break point opportunity while Svitolina continued to carve a number of opportunities for herself.
But it seemed nothing was going to stop Sasnovich as she made up for lost time at Brisbane.
In the quarterfinals of the Brisbane International Svitolina met with the ninth racket of the world Johanna Contoy.
Sasnovich apologised for her performance in the final, even though winning an eighth straight match at the tournament was a huge ask. I'm going to try to show my best tennis.
"Of course, (I was) exhausted". I just will be fight 'til the end. Everyone understands that it's a lot of matches, I understand it's a lot of matches.
She will head to Melbourne on Monday for the Australian Open after her continued success in Brisbane forced her to pull out of qualifying for the Sydney International. What can I say?