Oleksandr Dubinsky, from Zelensky's Servant of the People party, streamed the test live on the internet.
Earlier, Davyd Arakhamia, leader of the parliamentary faction of the president's party, had told reporters "we will go on a lie detector".
All MPs from the president's party who are also members of a special committee that examines draft legislation will be subjected to the test.
According to reports, MPs on the committee have allegedly taken bribes to block an anti-corruption law aimed at regulating the property market. The bill has not yet gone before parliament.
Zelensky on Wednesday called for the ten MPs involved to take the lie detector test.
So far, the lawmakers are not facing any charges but investigators have launched a probe after journalists and bloggers reported a possible crime.
If these checks find "even the slightest possibility that the lawmakers took the money... then the anti-corruption authorities should deal with these lawmakers," Zelensky wrote on Facebook.
Later Dubinsky, a member of the committee in question, was as good as his word and aired his lie detector test live on the internet.
"Did you personally vote against this bill in exchange for a bribe?" he was asked by an expert carrying out the test.
"Did anyone promise to pay you for a vote against this bill?" the expert continued, after the MP replied "no" to the first question.
It was not clear when all the deputies involved would take the lie detector test.
Zelensky, a former comedian, won presidential elections in spring on a programme promising to eradicate corruption.
According to Transparency International Ukraine is ranked 120th out of 180 on the NGO's corruption perception index, faring better than Russia (in 138th place) but still falling far behind its European Union neighbours.