Dubey first arrested the Knights' progress with a three-wicket burst on way to take a five-wicket haul for 24 runs.
Then he wielded his bat like a sledgehammer when the game was delicately poised, striking three sixes in the last two overs.
Thanks to Dubey's whirlwind 47 in 24 balls, and Bravesh Shetty's steady 60 not out in 51 balls, the Lions overhauled Knights' total of 152 with five balls to spare.
Triumph Knights got off to a superb start before Dubey removed the top three batsmen.
The pacer, who made his Ranji Trophy debut this season in the quarter-finals in Nagpur against Karnataka and picked up a fifer, nipped the first wicket stand between Praful Waghela (42) and Sumit Ghadigaonkar at 70 by dismissing the latter for 36.
Then he trapped the free-stroking Suryakumar Yadav in front for 35 after the Knights captain cracked two sixes and five hours in his 15-ball blitz.
Dubey accounted for Waghela, too, and Knights slumped quickly to 118 for 3 from 115 for 1.
Dubey, who was unsold in the IPL auction in January, got two more wickets in his second spell to help his side bowl out the Knights.
Later coming on to bat with his side on 94 for 3 in the 14th over, Dubey added 63 runs in 33 balls for the fourth wicket with Shetty to guide the Lions home.
The left-hander clouted Pratik Dabholkar for two sixes over long on in the 19th over and then struck Atik Attarwala off the first ball of the final over for another six to finish the game in style.
This was the Lions' first win in two games, while for the Knights it was their first loss after a victory in their opener.
Brief scores: Triumph Knights Mumbai North East 152 (P Waghela 42, S Ghadigaonkar 36, Suryakumar Yadav 35; S Dubey 5 for 24) lost to Shivaji Park Lions 157 for 3 (B Shetty not out 60, S Lad 30, S Dubey not out 47; V Bhoir 2 for 11) by seven wickets.
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