Krzysztof Piatek opened the scoring for the hosts before Andre Silva and a Kamil Glik own goal gave the visitors a 2-1 lead at the break.
Bernardo Silva scored a stunning goal to make it 3-1 seven minutes into the second half before Grosicki was introduced into the action on 64 minutes.
And the Tigers’ winger was involved in the goal that saw the Eagles drag themselves back into the game. After advancing down the right flank, Grosicki’s ball into the box was diverted into the path of fellow substitute Jakub Blaszczykowski who found the back of the net with an exquisite 77th-minute half-volley to set up a grandstand finish.
However, it proved to be nothing more than a consolation as Portugal held firm to condemn Poland to their first defeat under Jerzy Brzeczek.
Grosicki and his international team-mates return to UEFA Nations League action when Italy visit the Silesian Stadium in Chorzów on Sunday.