The out-of-favour India wicketkeeper stood like a pillar during his 128-ball knock (9x4), while opener K Bharath Shankar (58) and Baba Aparajith (68) contributed around him on an eased out Eden Gardens track to avoid an innings defeat after they resumed the day 128 runs in arrears.
Kathik completed his 21st first class century with a boundary off Abhimanyu Easwaran as both the teams agreed for a draw in the first over after the mandatory 75 overs with Tamil Nadu 327 for five under the fading lights on the fourth and final day.
The home team had a brilliant opportunity to secure an outright win after Sourav Sarkar dismissed nightwatchman R Aushik Srinivias in the sixth over of the day with addition of two runs to their overnight 82.
At that point the visitors still required 126 runs to avoid an first innings defeat as opener Bharath Shankar and Aparajith displayed showed a positive intent.
Shankar was bowled by Shukla after completing his half century but Karthik ensured that there was no further damage and stitched 103 runs in a crucial fourth wicket partnership with Aparajith.
Bengal used as many as nine bowlers including wicketkeeper Shreevats Goswami and skipper Laxmi Ratan Shukla credited Tamil Nadu batsmen for securing a draw.
"Overall, I'm happy with my bowlers' show and three points. We still have four matches to go and we're still positive (of making the quarters)," Shukla said.
The captain sustained a groin injury and was out of the field in the second session but he said there's nothing to "worry" about.
Tamil Nadu 246/9 and 327/5; 96 overs (Dinesh Karthik 103 not out, Baba Aparajith 68, K Bharath Shankar 58)
Bengal 454/9 declared.
Points Bengal 3, TN 1.
