A close affair saw the hosts dominate the first-half with Palace showing moments of grit that looked primed to be rewarded with progression, however they never quite matched the Hornets as the game wore on.
Those who watched the clash's opening few minutes may have predicted a visiting whitewash as Palace started things off as the brighter of the two sides.
Andros Townsend was first to set the onlooking crowd inhaling with expectation as he jinked along the left wing before chipping in a perfect cross towards the heart of Heurelho Gomes’ box, however no one in white was there to pick it up. He looked to repeat the threat seconds later and, having forced his way to the byline, was only prevented from doing so by former Eagle Adrian Mariappa.
Townsend was the man of the moment as the game kicked-off in top gear when, cutting inside on an initially overworked left wing, he rolled the ball to Luka Milivojevic, however the Serbian’s resulting shot wasn’t hit with conviction and Gomes toppled behind it to keep his goal guarded.
As the game slowed in the wind, the next threat from the visitors came on the opposite flank with Aaron Wan-Bissaka staying true to his roots as a winger and roaming up the pitch to latch onto a first-time Milivojevic pass before whipping in a ball to Batshuayi, who was just missed by the sailing cross.
For the first time in the game, Vicente Guaita was then called into action as Gerard Deulofeu skipped his way to the near post before unleashing a shot which cannoned directly off the Spaniard’s chest.
After a slow start, by this point the visitors had managed to secure a foothold in the game and sent a plethora of testing crosses from right to left and back again with each pinging clear of the Palace box after a nervy moment’s concern.
The concern proved valid minutes later when Watford opened the afternoon's scoring with yet another cross being posted over the Eagles' box and, with Guaita floundering to meet it, the ball landed at the feet of Etienne Capoue who, without hesitation, struck home into the unguarded net.
Guaita made amends almost immediately when Deulofeu looked to double the Hornets' lead, but at the near post Palace's shot-stopper displayed remarkable reflexes to tip his stinging effort over.
Deulofeu - the standout focus of the action - sent his fourth effort of the half hurtling towards Guaita when he looked to net from a 20-yard free-kick. Ultimately unaided by the required disruption from the interfering wind, however, the home side's Spaniard was unable to defeat the visitor's for the second time of the afternoon.
Max Meyer sought to reinstate the Eagles' dominance in the game but, having been chipped through by Wan-Bissaka, could only strike tamely at Gomes from six yards out.
After the re-start, it was Meyer again who looked to open Palace's account as he headed a bouncing ball downwards at Gomes' goal only to see the Brazilian 'keeper leap well to palm it away.
Townsend joined his teammate in midfield in looking to net when he struck a free-kick from a tight angle on the right which forced Gomes into action. Up next to try his luck was then Batshuayi as, pausing, he turned and swung at the Hornet’s goalmouth, but his effort flew barely a foot wide.
His work paid off on the second attempt, however, when from a similar position he calmly carried the ball into the box before slotting home emphatically into the rustling Watford net.
And upon connection between boot and ball, Vicarage Road was launched into life with the game immediately injected with the passion and energy of 3,000 vociferous south Londoners, the smoking smell of a cardinal red flare in its air and the constant, anthemic bouncing chants of the travelling faithful spurring its visitors on.
With the trademark stamp of a well-drilled Roy Hodgson side, however, the Eagles kept their cool and their focus while being buoyed by their jubilant equaliser and the renewed resolve they had mustered from the front went all the way through the team to the back, with Guaita pulling off two game-rescuing saves in his six yard box within three seconds of one another.
The level scoreboard would not go unchanged however as Watford regrouped after the equaliser and found their grip on the game once more. Tightening it, substitute Andre Gray then doubled their tally as he struck past Guaita to once again put Palace behind.
With a chance to extend their advantage, Watford were then denied by the out-stretched leg of Wan-Bissaka, who prevented Troy Deeney from netting the rebound after a Guaita save in the 84th minute.
Another heroic act of defence came from Palace's talismanic captain Milivojevic as he struck a ball from the goal-line to preserve the Eagles' hopes of a fight-back.
At the other end of the pitch, Wan-Bissaka was unfortunate to put wide the chance of his career when, with seconds remaining, he missed the goal from the edge of the box, however the opening was not quite as clear as he perhaps would have desired.
Ultimately, then, it was Watford who ended the afternoon as victors in spite of Palace's valiantly attempted fightback and it was the home support, standing triumphantly under a golden shower of suspended streamers, who earned a coveted trip to Wembley.
Watford: Gomes, Mariappa, Feminia, Cathcart, Holebas (Masina 45), Hughes (Gray 77), Doucoure, Capoue, Pereyra, Deulofeu (Cleverley 89), Deeney.
Subs not used: Dahlberg, Kabasele, Janmaat, Success.
Palace: Guaita, Schlupp, Kelly, Tomkins, Wan-Bissaka, Milivojevic, Kouyate, Townsend, Meyer, McArthur (Benteke 83), Batshuayi.
Subs not used: Hennessey, Woods, Ward, Riedewald, Wickham, Ayew.
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