The result leaves Inter level with Juventus on 39 points at the summit of the table but with a superior goal difference.
Inter Milan returned to the top of Serie A with a 1-1 draw at Fiorentina on Sunday but were denied victory by a superb late Dusan Vlahovic equaliser.
Former Fiorentina midfielder Borja Valero fired Inter in front after eight minutes, but Vlahovic carried the ball from inside his own half in stoppage time before smashing in a powerful finish.
The result leaves Inter level with Juventus on 39 points at the summit of the table but with a superior goal difference, while the late goal also eased the pressure on Fiorentina coach Vincenzo Montella.
Montella's side went into the game on a four-match losing streak, but a point moves them up to 13th place on 17 points.
Inter coach Antonio Conte thought his side deserved more than a point, and drew parallels with a 2-1 defeat to Barcelona at San Siro last week that guaranteed his side's elimination from the Champions League.
"These are games where we didn't take the results we deserved," Conte told Sky Italia.
"Against Barcelona, we paid for wasting several chances to score and allowing two situations where we could've done a lot better.
"It was a strong response from the team. It's disappointing about that late equaliser, because we deserved more, both tonight and against Barcelona. We must try to improve our finishing and our defending."
There was much at stake for both sides going into the game, as Fiorentina looked to arrest their slump in form and Inter targeted a return to the top of the table after Juventus moved ahead of them with a win over Udinese earlier in the day.
Montella's side face Roma on Friday in their final game before the winter break, and he insisted that he still feels he has the backing of the Fiorentina hierarchy.
"I will always be under pressure, that's the nature of the job," he said.
"If the club hasn't made that step so far, despite pressure from the outside, it means they believe in me.
"At the same time, I am well aware that four consecutive defeats are unacceptable."
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Valero, who spent five years at Fiorentina before joining Inter in 2017, showed great composure to turn inside his marker and fire a low finish in at the near post, but refused to celebrate against his former employers.
Inter goalkeeper Samir Handanovic performed a superb flying save to deny Milan Badelj, before the visitors came close when Lautaro Martinez's goal was chalked off for an offside in the build-up and Bartlomiej Dragowski clawed a Romelu Lukaku header off the line.
Lukaku threatened again in the second half when he shrugged off his marker to find space six yards from goal, but his shot was saved by the leg of Dragowski.
Vlahovic, however, stole the show in the 92nd minute when he gathered the ball near the halfway line, sprinted the length of the Inter half and fired a shot into the far corner from a tight angle to earn his team a precious point.