They now trail Bolton and have a game in hand as Posh look to build up momentum for the run-in.
Our photographer David Lowndes was on hand to capture these faces in the crowd pictures.
Take a look and see who you may know.
Get full reaction to the game, here.
1. Posh 5 Cobblers 1
Peterborough United fans enjoy the big win over Northampton Town. Photo: David Lowndes
2. Posh 5 Cobblers 1
Peterborough United fans enjoy the big win over Northampton Town. Photo: David Lowndes
3. Posh 5 Cobblers 1
Peterborough United fans enjoy the big win over Northampton Town. Photo: David Lowndes
4. Posh 5 Cobblers 1
Peterborough United fans enjoy the big win over Northampton Town. Photo: David Lowndes