Relegated after just one season in the top-flight, Watford then missed out on an automatic return to the Premiership last season despite being well ahead at the top of the Championship table at the beginning of the campaign.
Instead of gaining automatic promotion, Watford had to make do with a 6th placed finish in the Championship but in the play-off's they were well beaten by eventual winners Hull City at the semi-final stages.
Now, Boothroyd has left Watford by mutual consent because of a poor start to the current Championship season which was highlighted by last weekend's 4-3 home defeat to Blackpool which leave's the club hovering just above the relegation zone on goal difference in 21st place in the League table.
A statement on the club's official website from club chairman Graham Simpson reads:"Both parties feel his tenure at the club is simply at an end.
"It is with some sadness that we have taken the decision, along with Aidy, that the time is right for a new manager to take Watford forward.
"We have mutually decided that a parting of the ways is in the best interests of all concerned."