Warner also spared Sehwag's blushes as his opening partner was out after two balls, with Delhi chasing a challenging 187.
Such was the ferocity of Warner's hitting, Delhi matched Deccan's total with 20 balls left.
"We knew we had the batting line-up to chase the target, it was going to be a difficult chase but Warner was brilliant," said Sehwag, who was out for four.
"I was trying to hit it over long-on but failed to read the spin. Warner took the opportunity well. "
Warner's 109 not out featured seven sixes and 10 fours. He was in a 189-run unbroken stand for the second wicket with Naman Ojha (64 not out) at Rajiv Gandhi Stadium.
Warner hit a variety of strokes in only his second game for Delhi, after replacing Kevin Pietersen, the England batsman, who has returned home for a series against West Indies.
Playing pace and spin with ease, the Australia left-hander smashed 20 off an over from the pace bowler Ashish Reddy. He registered his second IPL century, after hitting 107 not out against Kolkata Knight Riders at Ferozeshah Kotla Stadium in 2010.
"It's a great feeling to be at the top of the points table and credit to the bowlers for the way they've bowled in this tournament," Warner said. "We knew that it [the ball] was going to move around, and we tried to take that away from them by going after the bowling very early."
Earlier, Shikhar Dhawan (84) and Cameron White (65) boosted bottom-of-the-table Deccan's innings. Dhawan clobbered five sixes and nine fours during his 49-ball knock, which included two consecutive sixes off the left-arm spinner Shahbaz Nadeem.
Dhawan added 126 for the third wicket with White but was run out to a direct throw by Nadeem from the square-leg boundary when he tried to take two runs.
The Australian White, who smashed two sixes and seven fours off 40 deliveries, followed a short while later when he skied a lofted shot and Naman Ojha, the wicketkeeper, took a fine catch running toward square-leg.
Kumar Sangakkara, the Deccan captain, could only praise Warner.
"He not only hit it hard, but very well, too; he took it away from us," the Sri Lankan said.
"It was a tough pitch for us to change from the previous wicket to this one. You do get pumped up sometimes, you need to keep calm and not let too much adrenalin through, which may not help sometimes."
Brad Hodge top scored for Rajasthan with 33 as they posted their lowest score of the competition.
Chennai made hard work of the chase. When Ravindra Jadeja was caught by Johan Botha off the bowling of Pankaj Singh, the Super Kings were six wickets down and still needed 43 runs from 22 balls.
Cue an explosion of runs from Albie Morkel, the South African, and Srikkanth Anirudha, who both hit 18 off just six balls to lead Chennai home. The match ended in an anti-climax, with the first ball of the 18th other, when Shaun Tait threw four wides on a free hit, having just been denied the wicket of Anirudha, who he bowled on a no ball.