The 100th league goal of Mauro Icardi's career couldn't stop Inter's winless run in Serie A stretching to five games, as a late Giovanni Simeone equaliser denied Luciano Spalletti's side a scrappy win.
The result means that Inter could drop down to fourth at the end of the weekend, with Napoli and Juventus moving closer to creating a true two-horse title race.
Fiorentina started the game by far the brighter of the two sides, young forward Federico Chiesa missing one golden chance when he swiped at a loose ball first time - oblivious of his clear path to goal.
The home side dominated possession in the first half and created the better of the chances, with Inter reduced to taking potshots from distance in order to give Marco Sportiello anything to do in the Fiorentina goal.
It was the visitors who opened the scoring though, Icardi racing in at the near post to head a free kick goalwards. Sportiello made a good save but could only parry the ball straight into the Argentina striker's path and - with no defenders tracking the run - was helpless to keep out the rebound.
The match was a much more even one than the reverse fixture on the opening weekend of the season, which saw Inter streak into a 2-0 lead before the break before adding the final touch to a 3-0 triumph shortly afterwards.
The difference between the games was more down to Inter's shortcomings than much in the way of improvement from La Viola, who failed to take advantage of some excellent positions in the attacking half before opening up at the back to allow Inter in at crucial times.
Samir Handanovic was called into action a couple of times late on, once to tip over a spectacular bicycle kick from Khouma Babacar, and looked as though he had done enough to earn his side three vital points until Simeone struck in the 91st minute after some penalty box pinball.