Parthiv, who struck 15 boundaries in his 98-ball knock, stitched a 104-run stand for the third wicket with opener Samit Gohel (38) to rebuild the Gujarat innings after the visitors were reduced to 29 for two at one stage at M Chinnaswamy Stadium.
Gujarat now trail by 90 runs with five first innings wickets intact.
At stumps, Bhargav Merai was batting on 41 while Akshar Patel was giving him company on six.
Earlier, Karnataka added another 80 runs today after resuming the day at 226 for seven with Ganesh Satish remaining not out on 75.
Satish, who hit nine fours and a six in his 137-ball unbeaten knock, shared 56 runs for the final wicket with the last man Sreenath Aravind (17) to take Karnataka score past 300.
Gujarat off-spinner Rakesh Dhurv scalped two more wickets today to return with innings figures of four for 83.
Brief Scores:
Karnataka 1st Innings: 306 all out in 104.1 overs (Ganesh Satish 75, Rakesh Dhurv 4/83).
