The home side fell behind against the run of play after 30 minutes but hit back quickly to equalise through Dan Hayes.
After the break, the Deans proved far more ruthless and coasted to a deservedly-emphatic win.
Hayes was on the mark once again to grab his second, with team-mates Mark Smith and Robbie Tambling also netting doubles on a day to remember for the home side.
‘We could easily have scored seven or eight,’ said Horndean manager Craig Pearce.
‘At half-time we spoke about being more ruthless and to be fair the players came out flying.
‘The important thing for us is to keep picking up points in our bid for a top-six finish.’
Moneyfields secured a second win in the space of 24 hours by beating Fawley 2-1 on the Waterside.
Manager Dave Carter made a few changes after the previous night’s hard-fought 1-0 derby win over AFC Portchester.
Carter introduced a few youngsters and it paid dividends as teenagers Declan Seiden and Ryan Pennery grabbed the all-important goals.
‘The youngsters I brought in did really well,’ he said.
‘That makes it just one defeat in our last 14 games and keeps on track for an unbeaten finish to the season.
‘It won’t be easy because we have another three games this week the final one being a cup semi-final against Baffins Milton Rovers.
‘There will be more juggling around with the squad this week with that in mind.’
Moneys have the chance of completing a quick-fire league double over Fawley as the two teams meet again at Dover Road tonight (7.45pm).