Inter were pegged back twice as Simone Inzaghi's 200th Serie A game as a coach ended in a frustrating 2-2 draw at Sampdoria.
Federico Dimarco's first Inter goal from an unstoppable free-kick was cancelled out when Edin Dzeko put Maya Yoshida's shot past his own goalkeeper at the Stadio Luigi Ferraris.
A superb Lautaro Martinez volley restored the lead only for an equally brilliant strike from Tommaso Augello to once again restore parity.
It means the champions have seven points from nine in their opening three matches and will look to regroup in the Champions League and a mouth-watering clash with Real Madrid.
Inter made a sloppy start and a poor Dimarco clearance led to a chain of events that saw Morten Thorsby wastefully head over the top.
Dimarco made up for that after 18 minutes with a venomous free-kick inside the D that picked out the top-left corner.
Sampdoria equalised when Yoshida's scrappy effort was diverted home via Dzeko after Inter failed to clear their lines at a corner.
Inter led at half-time when Hakan Calhanoglu dispossessed Mikkel Damsgaard and fed Nicolo Barella, whose sublime cross was expertly volleyed home by Martinez.
But they caught out again when Bartosz Bereszynski's cross was met with a rifling volley from fellow full-back Augello.
Shortly after, Ivan Perisic had a great chance to shoot or find Dzeko but really did neither when wastefully firing across goal, while Calhanoglu drilled wide from 20 yards with plenty of the goal to aim at.
Damsgaard almost put Sampdoria in front only for Danilo D'Ambrosio to clear off the line and rescue Inter.