Bologna's Brazilian forward Adailton side-footed home a cross deep in stoppage time to deny the Turin side, who had ridden their luck after French forward David Trezeguet prodded them ahead from close range on 24 minutes.
Juve are second with 14 points from six games, one behind Sampdoria, who beat Inter Milan 1-0 in Genoa on Saturday.
Champions Inter slipped two points off the pace to share third place with Fiorentina, who won 1-0 at struggling Livorno.
Udinese climbed to fifth, Serie A top scorer Antonio Di Natale setting them on their way to a 2-0 home win over Genoa with his eighth goal of the season.
Juventus went on the attack from kick-off and it was no surprise when Trezeguet struck as he had already twice come close to opening the scoring.
Bologna responded well and created a series of good chances before substitute Adailton gave them a deserved draw.
"It (the goal) wasn't the only chance they had. At times we were naïve when they took free kicks quickly," Juve coach Ciro Ferrara told Sky television.
"We gave away too much today. Maybe when we have the ball we don't manage it as well as we should, which means there are chances at both ends."
GOOD NEWS
The good news for Ferrara was that Brazilian playmaker Diego showed nice touches on his return from a hamstring injury before being substituted just before the hour.
Fit-again captain Alessandro Del Piero came off the bench in the closing stages to make his first appearance this term for Juve, who visit Bayern Munich in the Champions League on Wednesday.
Mid-table Milan can consider themselves lucky to be trailing Samp by no more than seven points as the southern visitors, who also held Inter 1-1 on the opening day, frequently had them on the back foot.
Bari midfielder Emanuel Rivas blazed wide after leaving a string of players floundering in his wake, while Milan keeper Marco Storari produced excellent saves to repel efforts by Leonardo Bonucci and Riccardo Meggiorini.
Milan coach Leonardo gave the inconsistent Ronaldinho a starting place at the expense of his off-form Brazilian compatriot Alexandre Pato, who came on in the second half.
The former Barcelona forward showed desire and had a crisp strike well saved in the 59th minute but he frequently found himself surrounded by markers as soon as he got the ball.
Napoli gave respite to under-fire coach Roberto Donadoni by beating Siena 2-1 at home with a Marek Hamsik double.
A stoppage-time Daniele De Rossi goal earned AS Roma a 1-1 draw at Catania, cancelling out Japanese striker Takayuki Morimoto's first-half goal.
Catania had Gennaro Delvecchio sent off as the match reached a bad-tempered conclusion.
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