Northampton's goal drought continued as Cardiff ran out winners at Sixfields.
A solitary Robert Earnshaw goal provided the promotion-chasing visitors with a comfortable win.
But the Cobblers have now failed to score or pick up a single point at home since mid-November.
They should have been chasing the game well before half time as Cardiff missed several good chances.
Earnshaw shot wide and volleyed over, Peter Thorne allowed Glyn Thompson to save at his feet and Graham Kavanagh hit the bar.
Marco Gabbiadini missed Northampton's best chance, rounding keeper Neil Alexander before Scott Young cleared the danger.
But it was Earnshaw who grabbed the decisive goal in the 58th minute with his 23rd league strike of the season.
Thorne's header came back off the bar and the Wales international was on hand to hook the ball home.
Northampton: Thompson, Gill, Hope, Reid, Carruthers, McGregor, Trollope, Rahim, Harsley, Gabbiadini, Asamoah. Subs: Stamp, Abbey, Burgess, Lincoln, Turner.
Cardiff: Alexander, Weston, Barker, Young, Croft, Bowen, Boland, Kavanagh, Mahon, Earnshaw, Thorne. Subs: Legg, Margetson, Bonner, Collins, Gordon.
Referee: R Olivier (Sutton Coldfield).