The 21-year-old Polish world No. 1 was dispatched by the French fifth-seed 1-6, 6-1, 4-6, leaving the home crowd disappointed.
The BNP Paribas Poland Open runs until Sunday, with Garcia due to face Italy's Jasmine Paolini in the semifinals on Saturday.
Świątek last Saturday helped raise more than PLN 2 million (EUR 425,000, USD 425,000) for Ukraine during an exhibition tournament in the southern Polish city of Kraków.
The Polish player last month won the French Open for the second time after defeating Coco Gauff of the United States in the final.
The 21-year-old, coached by countryman Tomasz Wiktorowski, in early April took over as the new number one in women's tennis, becoming the first Pole to top the world rankings.
The BNP Paribas Poland Open, first held last year, is the biggest tennis event in the country.
The WTA 250 tournament is part of the Women's Tennis Association tour and attracts some of the best female players from Poland and further afield.
(gs)
Source: TVP, PAP