Lewandowski’s late show keeps Barca’s chances alive, though the Blaugrana are now relying on Inter not to win either of their final two Group C matches.
Ousmane Dembele’s first-half strike put them ahead, though elimination was back on the cards as Nicolo Barella and Lautaro Martinez struck in a chaotic second half.
Robin Gosens thought he had sent Inter into the last 16 in the 89th minute, only for Lewandowski to score his second goal in the space of 10 minutes to snatch a point for Barca.
Henrikh Mkhitaryan cleared Lewandowski’s header off the line, while Edin Dzeko was denied by the crossbar in the opening exchanges.
Raphinha volleyed a glorious chance off target but made amends when he found Sergi Roberto, who drilled across for Dembele to turn home.
Gerard Pique inexplicably left Barella with space to smash past Marc-Andre ter Stegen five minutes into the second half, and Barca’s desperation was increased when Martinez’s strike clipped both posts before going in.
A deflected Lewandowski effort past Andre Onana dragged Barca back into the contest with eight minutes of normal time left, though they were staring down the barrel of elimination when Gosens finished past Ter Stegen following Martinez’s offload.
Yet Barca bought Lewandowski to deliver in decisive moments and the former Bayern Munich star powered home Eric Garcia’s cross in the second minute of stoppage time.
Kristjan Asllani should have won it for Inter, but was somehow denied by Ter Stegen’s feet as Barca clung on to their Champions League status for now.