The beleaguered India opening batsman, who averaged a pathetic 14.83 in South Africa, smashed 106 off 134 balls with the help of 15 fours as his side compiled a commanding 330 for seven at the close of first day's play of the Group A contest at Chaudhary Bansi Lal Stadium.
Sehwag's place in the Indian team has come under severe pressure following a prolonged form slump and he returned from South Africa with just 89 runs from six innings. But, today's century has put the swashbuckling right hander in the reckoning again for a possible inclusion in the squad for the forthcoming home series agianst the West Indies.
Taking cue of the fact that he achieved his only moderate success with a 40 against the Proteas batting down the order, Sehwag chose to come out at number four after Mayank Tehlan's fall when the scoreboard read 69 for two and sent the Haryana bowlers on a leather hunt.
After Sehwag called the coin correctly, Delhi began their innings on a shaky note with opener Gautam Gambhir and Mayank Tehlan falling cheaply for 16 and three respectively.
However, the other opener and Test prospect Akash Chopra (84) was rock-solid and shared a 112-run stand for the third wicket with Sehwag to deny Haryana any chance of taking control of the match.
Chopra's 84 came off 134 balls with the help of 10 hits to the fence.
Gambhir, who was also in the Test squad in the South Africa tour, was unimpressive as he faced 45 balls to make his 16 and had only one four in the 78-minute stay at the crease.
Former captain Mithun Manhas also failed to prosper and was run out for just one run.
Sehwag's departure at 244 for five led to a mini collapse with Puneet Bisht and Ashish Malhotra departing in quick succession with Malhotra out for a duck and Bisht scoring just six.
But Rajat Bhatia saw off the day with a fine unbeaten 55 which he compiled from 94 balls, hitting six fours and a huge six. Chetnya Nanda (29) was giving him company at draw of stumps.
For Haryana, Amit Mishra was the most successful bowler, claiming three for 67 while Joginder Sharma, S Budhwar and N Saini chipped in with one each.