Opting to bat first, Karthik was the lone significant scorer for Tamil Nadu as he slammed 14 boundaries in his 112-run knock to guide his side to a total of 217.
For Bengal, Mohammed Shami was the pick of the bowlers for his figures of four for 26 followed by Ashok Dinda's three for 36.Kanishk Seth also took a wicket.
In reply, an unbelievable disciplined bowling by Tamil Nadu bowlers restricted Bengal to 180 in their stipulated 50 overs, despite some good efforts by Sudip Chatterjee (58) and Manoj Tiwari (32).
While Aswin Crist, M Mohammed, Rahil Shah bagged two wickets each, Vijay Shankar, Baba Aparajith and Ravisrinivasan Sai Kishore all chipped in to defend a small total.
It was for the third time that Tamil Nadu prevailed over Bengal in the 50-over competition, having earlier beaten them in 2008-09 and 2009-10. (ANI)