For much of the campaign the Hornets have been involved in a battle to beat the drop, so the fact they ended it in 13th place shows the progress they have made since Brendan Rodgers took charge.
His troops had this game won by half-time, thanks largely to a brace from former Ram Grzegorz Rasiak and they had plenty of chances to add to their three-goal tally after the break.
After Barry Bannan had shaved the bar with a shot from the edge of the area, Watford got the ball rolling in the 14th minute.
Rasiak nodded the ball down to Tamas Priskin, who rather scuffed his shot, but it broke ideally for Jobi McAnuff to slide the ball low to Stephen Bywater's left for his fourth of the season.
The Hornets doubled their advantage 13 minutes later when, after Priskin had headed a Danny Rose free-kick against the bar and Adrian Mariappa had seen his acrobatic follow-up blocked on the line, Rasiak was left the simplest of tap-ins.
And Rodgers' men effectively put the game to bed four minutes before the interval, with the Poland international again showing his worth.
Indeed, the on-loan Southampton striker started the move that led to his second, finding Tommy Smith in acres of space to his right and then ensuring he was in the right place to capitalise on a low cross from the Hornets top scorer via the inside of Bywater's left-hand post.
Derby came more into the game after the break, with Watford seemingly content to settle with their lot for large parts, but when the visitors did threaten they looked destined to find no way past keeper Scott Loach.
He made an excellent reaction stop to thwart Kris Commons from close range after Derby's stand-out performer had been picked out by substitute Emanuel Villa.
But when the Rams did make the breakthrough, there was a degree of irony about the scorer - on-loan Watford midfielder John Eustace heading in a Bannan corner.