The measure passed in a 62-1 vote with no abstentions in the upper house of parliament on Saturday.
The legislation, which was earlier overwhelmingly approved by the lower chamber of Poland's bicameral parliament, now goes to the president for signing into law.
Under the cut proposed by the country’s government last month and now approved by parliament, personal income tax will be reduced for everyone earning less than PLN 85,528 (USD 22,537, EUR 20,087) a year.
The change is expected to come into force on October 1, benefiting 25 million taxpayers, public broadcaster Polish Radio’s IAR news agency reported.
President Andrzej Duda earlier this summer signed into law a plan by the country’s ruling conservatives to make people under 26 exempt from paying personal income tax.
Poland is due to hold parliamentary elections on October 13.
The governing conservative Law and Justice (PiS) party is seeking a second term in power after a landslide win in 2015.