Playing against Hyderabad at the Vivekananda College grounds, the 42-year-old Jadeja made a valuable 37 and added 75 runs for the fourth wicket with opener Sunny Singh.
The former India middle-order batsman rotated the strike well in his knock that included just two boundaries. Jadeja was caught by captain Akshath Reddy at cover point region of Anwar Khan's bowling.
Haryana mustered 215 for six in 38 overs in a rain-curtailed encounter after being put into bat.
Sunny was the top-scorer with 82 (77b, 7x4, 1x6), and opener Nitin Sainy chipped in with 36.
Hyderabad medium pacers C V Milind (2/42) and Anwar Khan (2/45) picked two wickets apiece.
In reply, Hyderabad were dismissed for 153 in 37.3 overs. Hanuman Vihari (45) and Amol Shinde (32) batted well for the team.
Haryana bowlers Ashish Hooda (3/12), Sanjay Budhwar (2/47), Kuldeep Hooda (2/34) and Rahul Tewaia (2/20) were among the wickets.
In other matches, defending champions Karnataka beat Bengal in Group-A, Kerala got past Baroda in Group-C, TNCA President XI disposed off Assam and TNCA XI defeated Uttar Padesh.
The highlights of the day included a six-wicket haul by India off-spinner Ravichandran Ashwin against UP and a strokeful century by Kerala opener Robert Fernandez (120 runs off 144b, 11x4s, 1x6).
Others centurions in the matches were Baroda opener Viraj Bhosle (102, 121b, 12x4, 2x6) and TNCA opener Bharath Shankar (102, 120b, 13x4, 4x6).
Group-A: Bengal 171 for 8 in 43 overs (Anustup Majumdar 58, Srivats Goswami 42 not out, Abhimanyu Mithin 3/9, K P Appanna 2/46) lost to Karnataka 173 for 1 in 37.5 overs, Abhishek Reddy 45, Ganesh Satish 58 not out, Manish Pandey 54 not out);
Group-B: Uttar Pradesh 279 all out in 78.1 overs (Tanmay Srivatsava 25, Prasanth Gupta 29, Mukul Dawar 38 retd.hurt, Akshadeep Nath 83, Praveen Kumar 36, Kuldeep Yadav 22, J.Kaushik 2/41, R.Ashwin 6/61) lost to TNCA XI 280 for 7 in 74.4 overs (Bharath Shankar 102, M Kaushik Gandhi 89 not out, Ashwin Venkataraman 34, V Maaruthi Raghav 33 not out, Kuldeep Yadav 3/98, Arish Alam 2/94);
Group-C: Haryana 215/6 in 38 overs (Sunny Singh 82, Nitin Sainy 36, Ajay Jadeja 37, Milind 2/42, Anwar Khan 2/45) bt Hyderabad 153 all out in 37.3 (Hanuman Vihari 45, Amol Shinde 32, Ashish Hooda 3/12, Kuldeep Hooda 2/34, Sanjay Budhwar 2/47, Rahul Tewatia 2/20);
Group-D: Assam 138 all out in 42.5 overs (J Syed Mohammed 49, Tarjinder Siingh 23, Sunil Sam 6/43, R Aushik Sriinivas 3/27) lost to TNCA President XI 139 for 5 in 42 overs (Indrajit Baba 40 not out, K B Arun Karthik 24, Arup Das 2/35)
Kerala 235 for 6 in 50 overs (Robert Fernandez 120, Vinoop Manoharan 38 not out, Vishnu Vinod 39, Lukman Meriwala 2/46, Aditya Vasava 2/45) bt Baroda 224 all out in 48.5 overs (Viraj Bhosale 102, Anupam Gupta 52, Nikunj Mohite 25 not out, L.P.Shahid 5/77, P.Prasanth 3/65 and Prasanth Parameshwaran 2/26).