Chasing a modest total, Bangalore started slowly and weathered the loss of openers Sophie Devine (32) and captain Smriti Mandhana (31) before Ellyse Perry (35 not out) and Richa Ghosh (17 not out) led them to victory in the final over.
Delhi captain Meg Lanning won the toss and chose to bat, the same decision she made last year when her team lost the final of the inaugural edition to Mumbai Indians.
Shafali Verma (44) and Lanning (23) started well with a blistering 64-run opening stand in seven overs before Sophie Molineux (3-20) put the stops on their charge with three wickets in four balls.
Sobhana Asha (2-14) and Shreyanka Patil (4-12) then chipped in with wickets at regular intervals to clean up the middle order and tail as Delhi collapsed and were dismissed for 113 in 18.3 overs.
Delhi's Shikha Pandey (1-11) and Minnu Mani (1-12) had some success in containing Bangalore's run rate in the first 12 overs, but Perry and Ghosh regained the momentum in the last five overs, to ensure victory.
"Finals are funny games," Molineux said after winning the player of the match award. "We knew it was going down to the wire."
While the Bangalore men's team have never won the Indian Premier League (IPL) title despite reaching the final three times, the women's team triumphed in the WPL's second season, ending the franchise's trophy drought.
"Bangalore fans are the most loyal... nothing could have happened without them," Mandhana said to the cheers of her team's supporters who were present in large numbers despite the game being held in Delhi.
"They have waited for this a very long time."
