Goals by strikers Marcelo Zalayeta and Zlatan Ibrahimovic and midfielder Pavel Nedved continued Juve's unbeaten start to the season and gave them 25 points from nine matches. AC Milan are second after beating Sampdoria 1-0 on Saturday.
Lecce, on 15 points, lie an increasingly distant third after their defence disintegrated in a 4-0 defeat to Fiorentina.
Chievo started strongly against Juve but when midfielder Manuele Blasi chipped the ball over their defence in the 24th minute, striker Zalayeta was ready in the box to turn the ball into the net for his fourth goal in five games.
Twenty minutes later the Uruguayan nearly set up Juve's second with a neat backheel to Nedved, but his shot was saved by keeper Luca Marchegiani.
Marchegiani was powerless to prevent Nedved scoring midway through the second half, though, when the Czech unleashed a vicious, dipping shot from outside the area.
Chievo striker Federico Cossato wasted a free header in front of goal and 11 minutes from time Ibrahimovic sealed the result when he muscled in front of defender Davide Mandelli and fired home a right-footed finish.
"I didn't think these kinds of results were possible," admitted a delighted Juve coach Fabio Capello. The win was his side's eighth in nine matches.
"We let our concentration slip a little with the score at 2-0 and we should be careful that it doesn't happen again, but overall I thought we played very well."
While Chievo's defeat was predictable, Lecce's capitulation in Florence was as swift as it was unexpected.
The southerners, who had shown great character midweek in overturning a two-goal deficit to draw 2-2 with Inter Milan, might have counted themselves unlucky when they went behind just before halftime to Martin Jorgensen's strike from wide on the right.
In the second half, however, they unravelled completely. Fiorentina midfielder Christian Obodo lobbed keeper Vicenzo Sicignano from just in front of the halfway line.
As Lecce's defenders pushed too far up field Obodo grabbed his second of the match and defender Giorgio Chiellini completed the rout with Fiorentina's fourth just before the end.
MONTELLA DOUBLE
Elsewhere, AS Roma made up for their midweek defeat by Juve with a 5-1 demolition of promoted Cagliari.
Cagliari were two down within six minutes as defender Traianos Dellas's diving header crept in at the far post and then Francesco Totti converted from the penalty spot after a foul on team mate Daniele De Rossi.
Striker David Suazo pulled one back for the visitors on the half hour but when Cagliari defender Francesco Bega failed to clear an innocuous-looking ball in the area shortly after the break Roma midfielder Simone Perrotta pounced to fire home Roma's third.
Two late goals by Vincenzo Montella completed the rout and took his season's total to eight, making him the leading scorer in Serie A.
In a later match Udinese were due to host promoted Palermo.
