MPs elected Horna-Cieślak in a 246-195 vote, with three abstentions, on Tuesday, Polish state news agency PAP reported.
Horna-Cieślak, a lawyer and children's rights activist, was backed by four opposition parties led by the liberal Civic Coalition (KO).
She previously ran campaigns for children's rights, worked with the Council of Europe on human rights education for legal professionals, and co-drafted some of Poland's legislation on children's rights, including a minors' protection law, the PAP news agency reported.
(pm/gs)
Source: PAP, TVP Info