Prime Minister Mateusz Morawiecki said on Twitter: “I would like to wholeheartedly congratulate Robert Lewandowski on his growing family.”
The head of government added: “One of my friends used to say: There’s only one thing more important than football in the world, and that’s family.”
Lewandowski scored a goal for his Bayern Munich side in its 2-0 Champions League win against Greek outfit Olympiakos on Wednesday.
In celebrating the goal, the 31-year-old Poland international tucked the ball underneath his jersey, sucked his thumb and gestured to indicate that he would become a father for the second time.
His wife, Anna Lewandowska, has confirmed that she is pregnant in a post on her Instagram account, Poland's PAP news agency reported.
The Polish prime minister, in his Twitter post, also congratulated Lewandowski on his “out-of-this-world form” as a goal scorer this season.
Lewandowski has scored in every Champions League and Bundesliga game this season for Bayern, bagging 20 goals from 14 matches.
The Pole, with 59 Champions League goals, is the competition’s fifth-highest all-time scorer, three goals behind France’s Karim Benzema.
Lewandowski in December 2016 celebrated his wife's first pregnancy after scoring for Bayern Munich in a Champions League clash with Atletico Madrid.