Before an audience which included Prime Minister Mateusz Morawiecki, she crooned her way to victory with a number carrying an environmental message called "Superhero."
It was Poland’s second win in a row in the competition, a feat no other country has managed before.
Following her success in the southern Polish city of Gliwice on Sunday, the emotional 12-year-old winner said: "I will be crying tears of joy for the rest of my life."
The contest was last year won by Poland’s Roxana Węgiel.
Held since 2003, Junior Eurovision is a song competition for youngsters aged between nine and 14 organised by the European Broadcasting Union (EBU) along similar lines to the Eurovision Song Contest, its older and bigger cousin.
This year’s event saw young performers from 19 countries trying their luck.
(pk/gs)
Source: TVP