Poland took the lead after 19 minutes when Bayern Munich striker Lewandowski, preparing for his first appearance at a World Cup, finished a team move with a precise strike.
The 29-year-old doubled his tally after the half hour mark from a free kick, following a foul on team mate Arkadiusz Milik. Lewandowski's strike cannoned off the bar and bounced out of the goal but the referee was informed by goal-line technology that the ball had indeed crossed the line.
Poland coach Adam Nawalka gave his talisman a rest at halftime, but the team continued to score in his absence. Sampdoria's Kownacki found the net after being set up by his club team mate Bartosz Bereszynski in the 71st minute.
Blaszczykowski completed the rout ten minutes later when he converted a penalty after the Video Assistant Referee signalled that Lithuania's Algis Jankauskas had handled the ball in the area.
Poland begin their World Cup Group H campaign in Moscow against Senegal on June 19, before facing Colombia and Japan.
(Reporting by Anna Koper; Editing by Christian Radnedge)
