After restricting the Pakistanis to 209 for seven in 47 overs, the Indians reached the target, 220 runs under the D/L method, in 44.5 overs.
Jadhav, who won the Man of the Match award for his effort, shared a 115-run stand for the third wicket with S Sriram (6) to set the stage for the win after India lost two crucial wickets of opener Gautam Gambhir (12) and M S Dhoni (15).
Gambhir was dismissed in the sixth over when he was caught behind by Kamran Akmal off strike bowler Riaz Afridi when the total was 24.
Twenty runs and six overs later, in-form batsman Dhoni returned to the pavilion, offering a catch to Misbah-ul-Haq off Afridi. Dhoni hit two fours during his 23-ball stay.
The wicketkeeper-batsman's dismissal saw Sriram joining Jadhav in the middle and the two plundered the opposition attack with some fine strokeplay.
After Sriram got out on 159, caught by Qaisar Abbas off Iftikhar Anjum, Ambati Rayudu (29 not out) came in and added 46 runs for the fifth wicket to take India closer to victory.
Jadhav, whose dismissal came when India were just 15 runs away from victory, faced 112 balls during his knock that was studded with seven fours and a six.
Earlier, put in to bat, Pakistan were in dire straits at 30 for four before a fighting partnership of 102 by Misbah-ul-Haq (89) and Mansoor Amjad steadied the ship, helping Pakistan to 207 for seven after the match was reduced to 47 overs.
All the three Indian fast bowlers -- Amit Bhandari, S S Paul and Avishkar Salvi -- were quite impressive as they shared six of the seven scalps between them.
Paul capped the tournament on a high returning with figures for three for 33 from nine overs. Bhandari took two wickets for 29 runs and Salvi one for 28.
Captain Sairaj Bahutule (1-50) accounted for the other Pakistani batsman to be dismissed.
Dhoni was named Man of the Series.