The 36-year-old goal machine, sidelined by a hamstring injury for the past four matches, including the high-stakes Copa del Rey final win over Real Madrid and last week's thrilling 3-3 first-leg draw with Inter, is now fully fit and has been named in Xavi's squad for the San Siro clash.
Lewandowski's return couldn't come at a better time. With 40 goals to his name this season, his presence could be the edge Barca need to punch their ticket to the final in Munich on May 31, where either Paris Saint-Germain or Arsenal await.
However, Barcelona's defensive options remain stretched. Left-back Alejandro Balde has failed to recover in time and will miss the trip to Italy. He'll now target a return in Sunday's LaLiga Clasico, again against Real Madrid. Jules Koundé is also ruled out after picking up a hamstring issue in the first leg.
Marc Casado is back in training but not match-fit, while Pablo Torre and Marc Bernal remain sidelined. Goalkeeper Marc-Andre ter Stegen remains ineligible for Champions League play.
With everything on the line and the aggregate score delicately poised, Barcelona will look to their veteran striker to deliver on the big stage once again.