The French fifth seed reached the final after seeing off Italy's Jasmine Paolini 6-1, 6-2 in the semifinals on Saturday.
A day earlier, Garcia dispatched home favourite Iga Świątek 6-1, 1-6, 6-4 in the quarterfinals.
Thanks to capturing her ninth WTA singles title, Garcia will advance 13 places to world No. 32 when the Women's Tennis Association releases its new rankings on Monday, Polish state news agency PAP reported.
The BNP Paribas Poland Open, first held last year, is the biggest tennis tournament in the country.
The event is part of the WTA 250 series and attracts some of the best female players from Poland and further afield.
(gs)
Source: TVP, PAP