Curtis Woodhouse netted a superb long-range goal to ensure Northwich's slump in form continued.
Woodhouse plundered the only goal of the game from fully 30 yards just after the hour to clinch the victory.
Only a fine performance from Northwich goalkeeper Phillip Senior prevented Rushden from further winning by more.
Danny Williams and Michael Rankin were denied by superb stops from Senior in the first half and Chris Hope's second-half free-kick was also saved.
Rushden & D'monds: Baker, Wilson (Beecroft 68), Albrighton, Hope, Watson, Lambley (Jackson 76), Savage (Wright 46), Woodhouse, Williams, Tomlin, Rankine.
Subs Not Used: Tynan, Hatswell.
Booked: Woodhouse.
Goals: Woodhouse 62.
Northwich: Senior, Battersby, Charnock, Roberts, Brown, Barwick, Byrne, Smart, Dean (Shaw 78), Roca (Williams 67), Townson.
Subs Not Used: Connett, Rutter.
Booked: Byrne, Roca, Battersby.
Att: 1,533
Ref: B Malone (Wiltshire).