Angel Di Maria crossed for Marquinhos to power in the opener after 11 minutes and then profited from some sublime Neymar trickery to double his side's tally before half-time.
Neymar played a huge part in PSG's comeback against Atalanta and should have registered inside 355 seconds of this tie, only to hit the post when played clean through.
The French side were boosted by the return of Kylian Mbappe to their starting line-up and he had a half-volley correctly ruled out a minute later for a handball against Neymar.
However, Leipzig could not settle and Thomas Tuchel's side were in front soon after when Di Maria's wicked delivery was guided in from six yards by an unmarked Marquinhos.
Neymar again clipped the post from a free-kick but he brilliantly set up Di Maria for PSG's second with a cushioned flick after Peter Gulacsi's pass was intercepted.
Leipzig brought on Emil Forsberg and Patrik Schick at half-time and started the second half on top, but Bernat met Di Maria's cross to head past Gulacsi and kill things off.
PSG had numerous chances to add a fourth in the remainder of the one-sided affair, with Mbappe squandering a good chance and then being denied by Gulacsi, who also produced a late double save to keep out Di Maria and Leandro Paredes.
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Di Maria undoes Leipzig
PSG may have missed Mbappe for three-quarters of their tight tussle with Atalanta yet the absence of Di Maria in that one cannot be understated.
He returned from suspension here and played a part in all three goals, taking his assists tally to 27 in the competition since his debut in September 2007 - only Cristiano Ronaldo and Lionel Messi (32 each) have more.
Gulacsi gifts goal to PSG
PSG looked dominant but undoubtedly were helped by some sloppy play from their opponents, with no error more glaring than Gulacsi's hospital pass in the lead up to the second goal.
The Leipzig keeper pretty much played the ball straight to Paredes, who fizzed it into the path of Neymar to tee up Di Maria with a superb flick.
PSG can now prepare for Sunday's showpiece final at this ground, where either German champions Bayern or domestic rivals Lyon await.