Adebayo Akinfenwa scored an injury-time equaliser to earn Northampton a point at Rotherham, who were playing their last game at the Don Valley Stadium.
Lewis Grabban crossed for Alex Revell to fire home the opener for the hosts but, despite their best efforts, they could not find a second.
Grabban struck a post and had a goal disallowed for offside, while Ben Pringle went close.
And they were made to pay when Akinfenwa headed home in stoppage time.
VIEWS FROM THE DRESSING ROOM
Rotherham United manager Steve Evans tells BBC Radio Sheffield:
"The performance was excellent.
"They (Northampton) have not had a worthy effort on goal, they've been outplayed.
"We lack a bit of quality in certain areas and that's why we're here and we'll work on that."
Northampton Town manager Aidy Boothroyd tells BBC Northampton:
"Today shows why we've managed to stay up. We've got the character to keep going and in the end, I thought it was a fair result.
"That's Adebayo Akinfenwa's 18th goal. He has a wonderful relationship with the fans and he's done everything I've asked him to do. I'm glad he's got his goal.
"I want to make sure we get a good squad together before we start pre-season."