Substitute Tyrell Richardson-Brown smashed home an 81st-minute winner as Horsham got a well-deserved three points to climb up to third in the Bostik League South East Division.
It took the attacking midfielder's late half volley to separate the sides in what was a well-contested clash at Culver Road between two teams jostling in the play-off positions.
And it was a deserved winner. The Hornets controlled much of the game and would have been kicking themselves had they not emerged with the three points after having a hatful of clear-cut chances in either half.
'Leafe, to their credit, played their part in an entertaining game and forced Horsham goalkeeper Josh Pelling into a couple of decent stops on the counter-attack.
But Tyler McCarthy was by far the busier goalkeeper in the third versus fourth-placed clash which saw both teams start the day level on 35 points.
By 5pm, however, it was the home side that had strengthened their play-off aspirations, narrowing the gap on second-placed Hastings United to three points as Surrey side 'Leafe dropped to fifth.
The hosts made one change from the side that won 2-0 at Faversham Town last weekend with Joe Shelley, fit again after his ban, coming into the line-up for Dean Lovegrove, who could find himself unlucky to just feature on the bench.
'Leafe, despite sitting third, went into the match in a patch of somewhat indifferent form - a loss, win and draw in their last three matches - and started the slower.
Within four minutes, Chris Smith had got goalside in the visitors' box and just as he was about to shoot a fantastic tackle from Corey Holder sent the ball out for a corner. Another neat move from a Charlie Harris interception followed. The midfielder passed into Smith, who flicked back to Harris and he drove forward into the box, but his effort was well held by a diving Tyler McCarthy.
On 15 minutes, Harris spread the ball out wide to Steve Metcalf and his cross went behind off a defender when under pressure from Rob O'Toole. Harris then won a free kick in his perfect range, but curled narrowly wide of McCarthy's left-hand post.
The first threat at the other end came on 21 minutes as wing-back Matthew O'Donoghue worked himself a yard of space in the box, but Pelling saved fairly routinely with a block using his legs. There were then big penalty shouts from the 'Leafe supporters and players as David Owusu-Akyeaw's back-post header was blocked out for a corner by Dylan Merchant, but referee Casimir Nzenga was unmoved. The resulting corner saw a bit of a scramble, but the ball went out for a goal kick.
After a quiet spell, Horsham almost broke the deadlock on 40 minutes through another well-constructed move. Having been worked down the left flank and back, a ball over the top put Harvey Sparks away, but his low, dangerous cross was blocked away by a defender with O'Toole waiting to tap home.
A free-kick from the corner flag was then headed goalwards by Merchant as O'Toole looked to help it on its way, but it was cleared off the line by O'Donoghue in the last action before half-time.
Things continued where they left off in the second half as a Lee Harding cross caused a moment of panic in the Whyteleafe box, before McCarthy hesitantly claimed it. A shot was flashed over at the other end, before Smith poked Sparks through one-on-one, but his tame shot was blocked by McCarthy.
Harris then tried to force the opener, beating two challenges and firing towards the bottom-left corner from 24 yards, but a full-stretch McCarthy tipped the ball around the post. Whyteleafe gave a gentle reminder that they were still able to counter-attack on the hour mark as the ball found its way through to Valentino Carpene, but Pelling made himself big to block his angled shot.
Horsham continued to control possession with Harris showing a wide range of passing to get them onto the attacking foot. Smith put an acrobatic shot wide and 'O'Toole, before at the other end, space opened up for O'Donoghue, but Pelling tipped his effort over.
Just when it started to look as though things would fade out into a 0-0 draw, Horsham substitute Richardson-Brown smashed home the opener in the 81st minute. A recycled corner was put back in first-time by Harris and while O'Toole went down under pressure from a defender with the fans appealing for a penalty, Richardson-Brown smashed home the loose ball on the half volley from 17 yards.
'Leafe, desperate for a leveler, pushed in the late stages, but came up against a well-managed final few minutes by the home side, who almost broke away a couple of times on the counter-attack,
Horsham: Pelling, Metcalf, Shelley, Merchant-Simmons, Sparks, Harris, Brivio (Lovegrove 65), Hayward, Harding, Smith (Richardson-Brown 75), O'Toole. Unused subs: Taylor, Kirkwood, Baxter.
Whyteleafte: McCarthy, Brand, Orome, Holder, O'Donoghue, Wilson, Akongo (Hattari 82), Graham, Ogobe (Armstrong 75), Owusu-Akyeaw (Chin 56), Carpene. Unused subs: McGeoghan.