The Scot, will take a perfect 12-0-0 record into the final eliminator against the 34-year-old Ukrainian.
"I can't wait to get back under those lights in Glasgow," said Taylor, 27, who is the WBC silver super lightweight champion .
"This is definitely my toughest opponent to date, and Viktor Postol should be the perfect test for me at this stage of my career.
"He's taken on and beaten some of the best fighters in the world, and I know he'll be coming here with the hope of spoiling the party.
"To know I'll be in line for a world title shot if I get the win has really put the fire in my belly, and you can expect to see the best Josh Taylor to date on June 23.
"The support in Scotland is always phenomenal, and I can't wait to make it another night to remember for everyone involved. See you all there."
Postol, a former WBC super lightweight title holder whose only defeat in 30 bouts was to Terence Crawford in a unification fight in 2016, said: "Taylor is a tough opponent and he had a good amateur career, he is a hard puncher as you can see from his pro record, and he changes stances throughout his fights so I will need to be sharp.
"The win in this fight against Josh Taylor will help me to approach my goal of becoming world champion once again.
"Taylor is a worthy opponent and I am fully focused on this fight! Let the best man win in Glasgow."
Taylor's promoter and manager Barry McGuigan said: "Josh Taylor truly is the real deal, and that shows when he's fighting someone as talented and experienced as Viktor Postol in just his 13th fight.
"We feel that this is the perfect final test for Josh before he challenges for world honours, and Viktor Postol will certainly not being coming to Glasgow to roll over.
"Both men are fresh, full of desire and ready to put it all on the line on June 23. This should be a cracker."
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