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.
9. Horndean's ZacK Willett tries an acrobatic attempt on goal
Horndean's ZacK Willett tries an acrobatic attempt on goal. Picture: Keith Woodland Photo: -
10. Fareham's Curt Robbins (red)
Fareham's Curt Robbins (red). Picture: Keith Woodland Photo: -
11. Horndean's Ben Anderson holds back Connor Underhill
Horndean's Ben Anderson holds back Fareham's Connor Underhill. Picture: Keith Woodland Photo: -
12. Fareham goalkeeper Luke Deacon saves from the feet of Connor Duffin
Fareham goalkeeper Luke Deacon saves from the feet of Connor Duffin. Picture: Keith Woodland Photo: -