The win, which Wim Koevermans' boys achieved without their skipper Sunil Chhetri, meant that India made it to their fifth successive final in the tournament and will meet Afghanistan in the final on Wednesday.
Mondal, the lad from Kolkata's Behala region, was a bundle of nerves throughout the match but turned out to be an unlikely hero in the end with a delightful strike.
The winner came in the 85th minute when Mehtab Hossain's corner from the right flank was neatly headed down by Syed Rahim Nabi and Mondal, who had joined the attack, struck a powerful angular right-footer that crashed into the net.
Maldives' striker Ali Ashfaq was tied down for most part of the match with India employing zonal marking with makeshift captain Gourmangi Singh giving a good account of himself. Maldives created a bit of pressure from set-piece movements giving some anxious moments to Indian custodian Subrata Paul.
Another anxious moment came in the 27th minute when Ashfaq's left-footed inswinging free-kick was nicely parried away by Paul.
It was a goalless first half but India played with some intent unlike their horrible show against Nepal. Jeje Lalpeklhua, operating from wide left, tried to make inroads while Arata Izumi, in central midfield, worked tirelessly helping in build ups and acting as a snatcher also.