The newly crowned I-League champions received an early jolt when opponent's Alwyn George was brought down inside the Aizawl FC penalty box.
Australian midfielder Cameron Watson scored the opening goal with ease from the penalty spot.
Bengaluru were without their star player Sunil Chhetri, who was ruled out of the game due to injury. Albert Roca fielded his team in the same 3-4-3 formation.
Sandesh Jhingan, Juan Gonzalez and John Johnson were the three centre-backs and Harmanjyot Singh Khabra and Salam Ranjan Singh played as the full-backs. Alwyn George, CK Vineeth and Eugeneson played upfront.
None of the teams could produce quality football in the first half as the score remained unchanged. Aizawl created quite a few chances but the Bengaluru defence were rock solid.
In the 39th minute, BFC got another chance and it was a golden opportunity. Cameron Watson attempted a long range shot which came off the post, unfortunately.
In the second half, Aizawl launched a series of attacks and the showed midfield domination under the leadership of midfield marshal Mahmoud Al Amnah.
The drama unfolded in the dying moments of the match when Aizawl got a penalty just 20 seconds before the final whistle.
Kamo Bayi was brought down inside the Bengaluru box and the referee straight away pointed towards the spot. But Amrinder Singh proved to be BFC's hero as he saved the penalty and guided Bengaluru FC to final.
Bengaluru will now face the winner of Kolkata derby in the second semi-final on May 21.