stretched their unbeaten pre-season record to five games thanks to Jermain Defoe's second-half header but it was a lacklustre showing at Vicarage Road on Sunday afternoon.
The 29-year-old striker found room in the box to head home Kyle Walker's cross after an excellent run down the right flank from the youngster.
But with just two weeks until the Premier League kicks-off, Spurs played vast periods of the game at walking pace in a match that may pose more questions than answers for Andre Villas-Boas.
The Portuguese boss welcomed Defoe back to the first-team after a family bereavement meant he left Spurs' US tour prematurely, while new signings Gylfi Sigurdsson and Jan Vertonghen were only named on the substitutes bench.
The game doubled up as a testimonial for Hornets' right-back Lloyd Doyley, and the early pace of the game signified as much.
In Tottenham's defence, they have just returned from the US and fatigue from a journey that began in Los Angeles and ended in New York may well have taken it's toll on the players.
However, the first period saw just one genuine chance created as William Gallas met Tom Carroll's in-swinging corner but planted his header just over Manuel Almunia's crossbar.
At the other end, ex-Spurs midfielder Mark Yeates controlled a diagonal pass, before twisting past Gareth Bale and sending a cross-shot towards the backpost that Brad Friedel managed to palm behind for a corner.
The visitors had plenty of possession, but where it mattered - in and around the box - their passing lacked precision and was easily dealt with by the Watford defence.
Villas-Boas experimented for most of the half by moving Bale to the right and Aaron Lennon to the left but the former didn't see anywhere near enough of the ball while the latter struggled to link-up with Defoe and the midfield.
At half-time, Villas-Boas made four substitutions, introducing Carlo Cudicini, Walker and the two new signings Sigurdsson and Vertonghen for Friedel, Kyle Naughton, Jermaine Jenas and Gallas.
And although their play marginally improved, their propensity for unnecessary long balls continued to concede possession to the hosts as well as frustrating a visibly agitated Villas-Boas.
But Walker was soon to put a smile on the Portuguese head-coach's face, as he collected a pass on the right-hand corner of the box on the 55th minute. Up against substitute Carl Dickinson, Walker used the space outside him to fly past and stand a perfect cross for the unmarked Defoe
to head home from six yards.
Watford may have felt aggrieved to have fallen behind and showed five minutes later that they still offered a threat to Spurs as Yeates latched onto a poor clearance from Cudicini.