Wrexham dented Rushden's promotion charge as the Welsh side bounced back to form after two poor results.
Leading scorer Andy Morrell grabbed a brace and Carlos Edwards had given Wrexham a good early lead.
It was a bad day for the Diamonds and Onandi Lowe added to their misery when he missed an injury-time penalty, as his spot-kick cleared the bar by two yards and landed among the visiting fans.
Manager Brian Talbot said: "We have a small squad and when we hadn't got our best 11 players out there, we have shortcomings.
"Wrexham took advantage and won convincingly and I thought their third goal was brilliant.
"We set out to keep a clean sheet and played defensively but after they scored, that was a waste of time. The penalty summed it up." A jubilant Denis Smith was in a happier mood after this win, following poor results against struggling Exeter and Swansea.
He said: "That was more like what we know we can play. Everybody did their job. We have conceded only one goal in five games and that is superb." Wrexham attacked from the kick-off and when the speedy Paul Edwards fired in a left-wing cross, Morrell jumped over it for Carlos Edwards to finish at the back post.
Lowe had a chance to pull a goal back when goalkeeper Andy Dibble fumbled an awkward bouncing ball in the blustery wind, but the Rushden striker fired his shot across the face of goal.
It was all Wrexham with corner after corner but they squandered chances as Carlos Edwards missed from close range and Morrell headed over.
Lee Trundle missed another opening when he beat two tackles and fired his low shot straight at goalkeeper Billy Turley.
Morrell got his first goal in great style when Carlos Edwards turned the ball across for him and he timed his finish perfectly, tucking the ball under the keeper.
The third goal was spectacular. Carlos Edwards fired a high diagonal ball across field, Trundle turned it into the middle and Morrell finished with a diving header that gave Turley no chance and had both sets of fans cheering.