Dutch forward Arnaut Danjuma scored the winner with a deft finish in the second half, but the game was overshadowed in the last few seconds as both Jack Wilshere and Joao Pedro were sent off for either side.
The result sees Bournemouth climb to 5th in the Championship table, while Watford remain 3rd.
Story of the game
Coming into the match, Bournemouth manager Jonathan Woodgate made three changes from the side that lost to Cardiff City in midweek, his first match as the permanent boss. In came Ben Pearson, Danjuma and Dominic Solanke, with Diego Rico and Philip Billing dropping to the bench and Sam Surridge omitted from the matchday squad.
Meanwhile, Xisco Munoz made two adjustments to his visiting Watford side, with Nathaniel Chalobah regaining his place in midfield having been rested against Blackburn Rovers in midfield, and former Cherry Dan Gosling thus beginning the afternoon on the bench. Craig Cathcart also came into defence in place of William Troost-Ekong.
It was a quick start from Munoz's in-form men, who had Bournemouth pinned in the own half for most of the opening five minutes. The Hornets had their first chance of the match when Ismaila Sarr stung the palms of Asmir Begovic, and the goalkeeper could only parry the ball as far as Adam Masina whose header in turn went just wide of the near post.
The hosts weathered an early mini-storm and eventually got a foothold in the game. They fashioned the next opportunity, with Junior Stanislas picking the ball up around 25 yards from goal before setting himself and taking aim at goal, but Francisco Sierralta produced a fine block to save Daniel Bachmann making the stop.
Bournemouth could have opened the scoring just past the 20-minute mark, but for a crucial intervention from the Watford defence. A sumptuous turn from Solanke worked him some space in midfield before the striker fed Stanislas through on goal. He sent Sierralta to the floor and lined up a shot, but Masina summoned up an inch-perfect tackle and Bachmann could claim.
Moments later, good link-up between Sarr and Kiko Femenia set the latter away to drove towards the byline. He crossed into the centre where Joao Pedro was lurking, and it seemed for all the world that he would score until his header soared just past the near post; a real let-off for Bournemouth.
With 30 minutes on the clock, we saw a goalkeeper forced into a very good save for the first time in the match. Liam Kelly picked up possession on the left edge of the penalty area and unleashed a vicious drive towards the far top corner, but Bachmann got across brilliantly well to tip the ball over the bar. Steve Cook headed over from the resultant corner.
There was a good tempo to this game to end the first-half. Sarr turned on the edge of the box before teeing up Will Hughes to strike from about 25 yards out, but the midfielder failed to trouble Begovic. Sarr had the final chance of the first 45 minutes with a dipping shot from just outside the area which again sailed just high of the target.
It was both defences who had so far come out on top in this crunch clash; something would need to give in the second period.
Scrappy was the byword in the opening few exchanges following the restart. Both Lewis Cook and Hughes went into the referee's book within a matter of minutes, but Watford soon got their foot on the ball. A threatening cross from Femenia forced Begovic into an awkward save with Pedro ready to pounce just behind him.
Bournemouth attacked next as Danjuma waltzed into the Watford box and struck at goal from an acute angle, but Femenia put his body on the line to block the ball. The Dutch winger was then set through on goal again by Jefferson Lerma and attempted to drive the ball beneath Bachmann, but the Austrian shot-stopper got down well to save.
It was all happening down that flank, with Bournemouth's left and Watford's right side heavily involved in pretty much every sequence of play.
Next, Sarr drove infield and thread a ball into Tom Cleverley darting behind the Bournemouth defence, and the midfielder produced another super save from Begovic akin to that made by Bachmann moments earlier.
This game was balanced on a knife-edge, and a goal always seemed inevitable. It came right on the hour mark when Danjuma, ever so lively in this half, squeezed the ball home from a tight angle after incisive build-up from Bournemouth. It wasn't Bachmann's finest moment, letting the ball in at his near post, but it was a good finish from Danjuma whose contribution certainly warranted a goal.
Watford needed to respond, their four-game winning streak now under considerable threat. Again they looked to the talismanic Sarr, who touched the ball intelligently past Kelly and attempted to drive the ball home at the near post, but it was just wide of the target. The Senegalese forward then attempted to latch onto a through-ball from Ken Sema, but Begovic just got there ahead of him.
It felt like Watford's best chances might already have gone begging, Bournemouth having been imperious in defence all game long and clinical with their one best opportunity. Substitute Achraf Lazaar looped a hopeful header wide after a set-piece, but that was their best chance.
Tempers flared in the final few seconds of the match. Substitute Wilshere and striker Pedro were dismissed for Bournemouth and Watford respectively, both being dealt their second yellow cards.
Takeaways from the match
Danjuma inspires Cherries
Fairly quiet in the first-half, but very much the difference maker in the second — for about 20 minutes after the restart Watford simply couldn't contain Danjuma and he very much deserved his goal having been Bournemouth's most effective attacker in what was a performance dominated by the solidity of their defence.
Clinical edge missing for Watford
This wasn't necessarily a game the Hornets deserved to lose; they got into a number good positions but didn't manage to trouble Begovic once in the first-half and failed to creative quite as much after the break. This result is by no means a disaster, but it is a set-back after a good spell of form, and discipline may be a cause for concern, though that could be said for both sides.
AFC Bournemouth: Begovic; Smith, Carter-Vickers, S Cook, Kelly; L Cook, Pearson (Billing 85'), Lerma; Stanislas (Wilshere 74'), Solanke (Long 79'), Danjuma.
Unused subs: Travers, Mepham, Rico, Kilkenny, Riquelme, Anthony.
Watford: Bachmann; Femenia, Cathcart, Sierralta, Masina (Lazaar 74'); Cleverley, Hughes, Chalobah (Gosling 74'); Sarr, Pedro, Sema (Perica 82').
Unused subs: Elliot, Ngakia, Troost-Ekong, Wilmot, Zinckernagel, Gray.
Referee: Tony Harrington
Following victory here, Bournemouth travel to Bristol City, the new home of former Watford boss Nigel Pearson, on Wednesday evening.
Watford return to their home of Vicarage Road to face low-lying Wycombe Wanderers on the same day.