With the 90 minutes up, and the hosts leading 1-0 through Igor Budan's 56th-minute goal, Inter faced the prospect of handing their bitter city rivals AC Milan the chance to win the title on Sunday at the San Siro.
Anything other than a win over Cesena would have meant a victory for Milan at home to Bologna would be enough to see the rossoneri crowned league champions for the 18th time.
But instead substitute Pazzini turned the game on its head in a most unlikely and stunning finale.
It means Inter closed the gap to five points and left Milan still needing four points to be crowned champions.
It was more than Inter deserved after possibly their most listless performance this season in which they created almost nothing until the 90 minutes were up.
For Cesena it was deeply disappointing after they looked set to go five points clear of the relegation zone.
The first half was a disappointing affair with only one chance of any note, going the way of the hosts early on.
Emanuele Giaccherini burst onto a dinked ball over the top and headed on but the diminutive striker faced a race to the ball with Luca Castellazzi.
Although he got there first he couldn't quite stretch his leg out far enough to prod the ball over the Inter goalkeeper who blocked.
It was again the hosts who had the better of things after the break as former Inter attacking midfielder Luis Jimenez created problems.
A first effort from the right was parried by Castellazzi at his near post while the Chilean flashed wide a second on the volley from the same spot.
Cesena got the lead their industry deserved on 56 minutes but it was in no small part thanks to some poor defending from Inter.
The overlapping Luca Ceccarelli was allowed to run free down the right behind Japan full-back Yuto Nagatomo and he sent over an inviting cross into the centre of the box.
Lucio was drawn to the near post where his centre-back partner Andrea Ranocchi already was and both missed the ball allowing Budan to volley home unmarked from eight yards out.
A mark of Inter's ineptitude was highlighted by the fact they reached the 90 minute mark with only two half-hearted efforts from Lucio to show for their efforts.
In the dying moments Cesena substitute Dominique Malonga wriggled into the box and then saw his shot deflected behind for a corner as he tried to put the icing on the cake.
But what happened next was as unexpected as it was stunning.
Suddenly in injury time Samuel Eto'o sent an inswinging cross into the box and Pazzini got in front of his marker to poke home on the volley.
And moments later he rose again in the box to head home Maicon's cross from the right for the most dramatic turnaround.