Luke Guttridge's header saw off AFC Wimbledon as Northampton picked up only their second home win of the season.
The Cobblers dominated early on as Guttridge drew a save from Seb Brown, with Adebayo Akinfenwa heading over from the resulting corner.
Clarke Carlisle had a header cleared off the line, while Jason Euell missed two chances for the visitors.
Guttridge nodded the winner after Brown could only deflect substitute Toni Silva's shot into his path.
The goal handed Northampton their second win in 18 league matches.
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Northampton Town manager Aidy Boothroyd tells BBC Radio Northampton:
"I'm pleased, I know our fans are pleased and it's a deserved win as well.
"Psychologically, I think a clean sheet is worth four points. My fears were that we were so desperate to win that we might get caught on the counter-attack.
"It's about getting points on the board. I think our energy and form are on an upward curve.
"Luke Guttridge said to me when he signed that he'd get goals and that we won't go down with him in the team, and I think he's right."