Only trailing for two minutes of the match, the Cats were pushed all the way by Hawthorn, who threatened to steal a famous win.
But a crucial turnover by Josh Weddle in Hawthorn's defensive 50 led to Shaun Mannagh kicking his third goal with three minutes left, giving the Cats a seven-point advantage.
Hawks skipper James Sicily had a set shot moments later in a bid to cut the deficit back to one point, but failed to score.
Geelong's 12.14 (86) to 11.13 (79) victory moved them to 4-2 this season, leaving the Hawks with a second-straight defeat following their shock Gather Round loss against Port Adelaide.
It was the largest home-and-away crowd Geelong have played in front of and broke the Easter Monday record set in 2008.
Hawthorn midfielder Conor Nash is facing a hefty suspension after striking Gryan Miers, leaving the Geelong dynamo staggering from the field in the third term.
Nash tried to make a physical impact on the contest when Miers had the ball, but his arm stayed high and collected his opponent in the head.
Miers was subbed out immediately and has entered the 12-day concussion protocols, causing him to miss at least Sunday's clash with Carlton back at the MCG.
Nash was reported on the spot by the field umpires and could be suspended for as long as four weeks.
Geelong star Bailey Smith continued his run of riling up opponents and crowds when he randomly slammed the ball into the head of Hawthorn defender Jarman Impey in the second term.
Smith could also be scrutinised over a hand gesture directed towards Hawthorn fans when he was jeered while running off the ground.
The latest incidents came little more than one week after Smith was fined $1000 for flipping a "double-bird" at an Adelaide fan who was taunting Geelong captain Patrick Dangerfield as the team walked off the ground.
The 24-year-old was jeered by Hawthorn fans - and cheered by Cats supporters - for the rest of the game every time he touched the ball after the unusual interaction with Impey.
But Smith managed to have the last laugh, being Geelong's leading possession-winner with 28.
Jack Gunston and Mabior Chol fired up forward for Hawthorn with three goals each.
Veteran Gunston could have had an even bigger day, kicking two shots out on the full and missing another gettable opportunity.
Geelong captain Patrick Dangerfield continued his brilliant start to the season as a forward, kicking three goals, including an important major in the last quarter, to take his season tally to 14.
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