The Punjab captain, returning to action after recovering from an abdomen injury, compiled an unbeaten 64 in a total of 4-123 in 16.3 overs.
The team's seamers of Praveen Kumar, Parvinder Awana and Azhar Mahmood had earlier taken two wickets each to restrict Chennai to 7-120 on a lively pitch at Himachal Pradesh Cricket Association Stadium.
Gilchrist, who also took four catches behind the stumps, struck two sixes and nine fours in 46 deliveries to see his team through with ease.
"It was good to take the field," the Australian said.
"It was one of those days when the Chennai batsmen nicked all of them, all of them straightforward catches."
West Indian allrounder Dwayne Bravo fought a lone battle, hitting three sixes and two fours off 43 balls before falling to Ryan Harris in the last over of the innings. He struck David Hussey for two consecutive sixes - straight down the ground and over the mid-wicket fence.
Bravo also took two wickets later in the day.
Punjab have eight wins and seven losses with one more match to go against the already qualified Delhi Daredevils.
Chennai finished the preliminaries with eight wins, seven losses and one no-result and other match results will determine their fate.
In Thursday's late match in New Delhi, Chris Gayle produced a blistering 128 not out as Royal Challengers Bangalore beat the Daredevils by 21 runs at Ferozeshah Kotla Stadium.
Gayle bludgeoned 13 sixes and seven fours off only 62 balls and partnered in an unbroken double century stand with Virat Kohli (73) as Bangalore amassed 1-215. Delhi scored 9-194 in reply with Ross Taylor producing a valiant 26-ball 55.
Gayle scored only one run off the first nine deliveries he faced, but launched a relentless attack that included three consecutive sixes off left-arm spinner Pawan Negi and three sixes in an over by Irfan Pathan.
It was Gayle's third IPL century and the second highest IPL score after Brendon McCullum's 158 not out for Kolkata Knight Riders against Bangalore in the first match of the inaugural edition in 2008.
Gayle and Kohli added 204 in what is the second highest partnership in five seasons of IPL and came exactly one year after Gilchrist and Shaun Marsh established the record of 206 for Punjab versus Bangalore last year.
Delhi qualified for the playoffs with wins and five losses from 15 games.
Bangalore have eight wins, six losses and a no-result.