For Rajasthan, barring two-down Rajesh Bishnoi (23), no batsman showed spine as the southern outfit grabbed wickets at regular intervals to restrict it to 112 for nine.
A patient unbeaten 22 by number nine batsman Ravi Bishnoi helped Rajasthan cross the 100-run mark. For TN, all-rounder Vijay Shankar (2-13) was the pick of the bowlers.
Tamil Nadu then rode on a gritty unbeaten 54 by all-rounder Washington Sundar as it overhauled the target with 2.1 overs to spare.
Sundar played a responsible knock as he held the innings from one end.
India's key spinner R Ashwin, in a surprise move, opened the batting and scored valuable 31 runs off 33 balls.
After Ashwin departed, Sundar took the side home.
Earlier, in the first semi-final, pacer Abhimanyu Mithun, openers Devdutt Padikkal and K L Rahul starred as defending champion Karnataka romped into the final thrashing Haryana by 8 wickets in the first semi-final.
The highlight of the Karnataka-Haryana match was Mithun (5/39) taking five wickets in an over including a hat-trick and registering his name in the record books. Mithun became the first bowler in the domestic circuit to claim hat-trick in all the formats.
He had snared a hat-trick in the Vijay Hazare (national ODI championship) final against Tamil Nadu earlier this year.
BRIEF SCORES: Haryana 194/8 (Himanshu Rana 61, Chaitanya Bishnoi 55; Abhimayu Mithun 5-39) lost to Karnataka 195/2 (Devdutt Padikkal 87, K L Rahul 66; Harshal Patel 1-28);
Rajasthan 112/9 (Rajesh Bishnoi 23, Ravi Bishnoi 22 not out; Vijay Shankar 2-13) lost to Tamil Nadu 116/3 (Washington Sundar 54 not out; R Ashwin 31; Deepak Chahar 1-11)