And they triumphed despite having to play most of the second half with only 10 men after skipper Garry Moody was sent off for a foul on Ben Anderson.
Six of the goals were shoehorned into the first 45 minutes - Fareham leading 4-2 at the interval thanks to Curt Robbins, Josh Benfield and Jack Breed (2).
Sam Hookey had levelled for the Deans, who had won 12 and drawn twice since their only previous Wessex Premier loss of the season, 1-0 at Hythe on September 3. Connor Duffin also replied just before half-time.
Though having a numerical advantage, the Deans had to wait until late on in the second period before Harry Jackson completed the scoring.
25. Horndean'sr Fuzz Kanjanda collides with his manager Michael Birmingham
Horndean'sr Fuzz Kanjanda collides with his manager Michael Birmingham. Picture: Keith Woodland Photo: Keith Woodland
28. Jack Breed celebrates one of his two goals
Jack Breed celebrates one of his two goals. Picture by Ken Walker Photo: Ken WALKER