After sending in Bengal and restricting them to 136, Jharkhand began their chase with intent, as openers Ishan Kishen (30) and Saurabh Tiwary (29 off 19 balls) raised 63 runs.
But, Tiwary's dismissal in the eighth over triggered a collapse as a wicket fell in each of the four overs that followed with the addition of only 13 runs. Captain Laxmi Shukla (3 for 15) and Veer Pratap Singh (2 for 19) were instrumental in causing the slide.
Bengal's chief contributor with the bat was Debabrata Das, who top-scored with a 33-ball 61, while Jharkhand's Vikash Kumar and Shahbaz Nadeem picked up two wickets apiece.
In another East Zone match, Tripura beat Assam by six wickets with five balls to spare, riding on Yogesh Takawale's unbeaten 68 off 49 balls.
Tripura chased down the target of 173 with Takwale and Sanjay Majumder (39) shared 88 runs off 10 overs for the third wicket to help their side reach the target.