In a disappointing opening half the first near effort came in the 27th minute when Shrewsbury should have taken the lead as Kelvin Langmead shot wide after being put through by Jamie Tolley.
Greg Pearson could have scored for Rushden 10 minutes later when he miss hit a cross from Chris O'Grady and, on 40 minutes, Shrewsbury defender David Walton saw his header saved by veteran keeper Andy Woodman.
The game changed dramatically with the introduction of David Bell on the right-hand side of Rushden's midfield and he made an immediate impact when he cut in from the right and crossed for skipper Dave Savage to fire home from 10 yards out on 49 minutes.
Rushden increased there lead in the 65th minute when Bell ran fully 30 yards at the Shrewsbury defence and unleashed a tremendous left-foot shot from 20 yards out which left keeper Joe Hart helpless.
Rushden began to run the game and only a brilliant save from Hart denied Rob Gier after a fine move.
Rushden continued to press forward but were denied by further good saves from Hart, but they eventually put the game beyond doubt in the 85th minute when Chris O'Grady volleyed home after more good work by Bell.
Despite a late rally by Shrewsbury the Rushden defence held firm to gain a deserved victory. The points were valuable for Rushden and eases there relegation fears.