Midfielder Bernardo Silva opened the scoring for the visitors from close range in the 26th minute of the game at the National Stadium in Warsaw.
Captain Cristiano Ronaldo made it 2-0 for Portugal after taking advantage of a gap in the Poland defence 11 minutes later.
Poland's Inter Milan midfielder Piotr Zieliński narrowed the deficit to 1-2 in the 78th minute when he smashed the ball home from inside the box after an error by the visiting team's defence.
But an own goal from Poland defender Jan Bednarek set the final score at 3-1 for Portugal in the 88th minute, leaving the hosts unable to stage a comeback.
The Polish team had few scoring opportunities in either half of the match, and its star striker Robert Lewandowski failed to register a shot on target.
The Poles, captained by Lewandowski, failed in their plan to put up a strong performance against their higher-ranked opponents on home turf.
Photo: PAP/Leszek Szymański
Poland are ranked 30th worldwide by football's governing body FIFA, while Portugal are No. 8 in the FIFA table.
Before the match, two former Poland players, goalkeeper Wojciech Szczęsny and midfielder Grzegorz Krychowiak, were given an official send-off after retiring from the national team.
Szczęsny, who recently joined Spanish giants Barcelona, earned 84 caps with Poland, while Krychowiak reached 100.
At a pre-match news conference on Friday, Poland manager Michał Probierz said that the team's National League games against top opponents "have exposed some shortcomings that need to be addressed."
Probierz has previously said that this season's Nations League offers a valuable opportunity to assess players and prepare them for 2026 World Cup qualifiers.
Poland boss Michał Probierz speaks to reporters at a press conference in Warsaw on Friday, Oct. 11, 2024. Photo: PAP/Leszek Szymański
Poland opened its Nations League campaign by defeating Scotland 3-2 in Glasgow last month. The Polish team was then beaten 0-1 by Croatia in its second game in Group 1 of the top League A.
After three rounds of fixtures, Poland are third in their Nations League Group A1, with three points.
Poland will take on Croatia in Warsaw in their next Nations League fixture on Tuesday.
The Nations League is the European football governing body UEFA’s newest national-team competition that is now in its fourth edition.
Portugal won the first edition of the Nations League in 2019, while France won the 2020/2021 UEFA Nations League, and Spain triumphed in the 2022/2023 edition.
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Source: IAR, PAP, TVP