A goal in each half was enough to give Dereham the edge in a close game at Aldiss Park.
Both team won corners in a competitive start and in the 12th minute Heybridge's Guillan Ramon delivered a cross from the right that reached Juan Luque but he fired over the top whilst under pressure from home defender Matt Castellan.
The Magpies won a free-kick 30 yards out, with Danny Beaumont's drive deflected to visiting keeper Danny Sambridge.
Soon after Dereham won another free-kick that skipper David Hinton floated into the box with the loose ball falling to Castellan, whose close-range effort was blocked.
Dereham then missed an opportunity when Castellan fed Sam Borrer down the right. The midfielder cut inside and after keeper Sambridge had saved his initial drive, he put the rebound over the top.
As the hosts pressed again good play from Ryan Crisp created another opening, but Dereham finally made the breakthrough in the 40th minute. Following an excellent build-up involving Crisp and Jamie Forshaw, the ball was threaded through to Rhys Logan who made no mistake from close range to give them an interval lead.
Heybridge responded, but Robbie Linford thwarted Joe Gardner with a great challenge. Magpies keeper Elliot Pride was then forced to produce an excellent save to deny Ben Griffiths before Dereham countered, Logan finding Forshaw whose low drive was diverted for a corner from which Castellan rose well to head home and increase Dereham's advantage in the 70th minute.
Heybridge reduced the arrears six minutes later when Gardner scored from close range and only a great save from Pride, who turned Ryan Henshaw's drive around the post, preserved Dereham's lead.
Dereham: Pride, Castellan, Anema, Hinton, Eastoe-Smith, Linford, Logan (Murphy 82), Borrer, Crisp (Jarvis 65), Forshaw, Beaumont.
Subs not used: Howell, Fitch.
Heybridge: Sambridge, Ramon, Cooney, Dark (Godbold 86), Henshaw, Stevenson, Chatting, Griffiths, Callander, Gardner, Luque.
Subs not used: Smith, Conway, Morgan.
Ref: D Hutton. Att: 132
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