West Ham pipped Reading to the play-offs after beating Watford away.
Goals from Anton Ferdinand and a Marlon Harewood penalty ensured Alan Pardew's side claimed sixth spot, setting up a play-off semi-final against Ipswich.
After Watford failed to clear a corner, Elliot Ward's cross from the left found Ferdinand, who volleyed home.
A handball by James Chambers allowed Harewood to score with a penalty, with a late spot-kick from Heidar Helguson pulling a goal back for Watford.
Last season West Ham also reached the play-offs, losing out to Crystal Palace in the final after beating Ipswich over a two-legged semi-final.
At the start of Sunday, West Ham and Reading had been tied on 70 points and were level on goal difference.
With so much to play for Alan Pardew's side were quickly on the offensive, Shaun Newton's fierce drive from the edge of Watford's penalty box fizzing inches wide after just four minutes.
West Ham' s play visibly relaxed as news filtered around Vicarage Road that Wigan had scored twice against Reading early in the first half.
But the opening goal continued to elude the visitors, helped in part by some wayward finishing.
Bobby Zamora somehow scuffed wide a superbly-worked set-piece shortly after the half-hour mark, while Harewood forced Alec Chamberlain into a fine reflex save from close range.
Finally three minutes before the break West Ham made the breakthrough.
Ward chipped the ball into a packed penalty area for Ferdinand to let fly with a well-executed volley that angled into the corner of the net via a slight deflection.
Watford began the second half brightly, and fashioned their best chance of the game when Hameur Bouazza's header off Ashley Young's cross arrowed just left of James Walker's right-hand post.
West Ham maintained the upper hand, however, and stretched their advantage from the penalty spot after 70 minutes following James Chambers' needless handball.
Andy D'Urso had no option but to point to the spot and Harewood did the rest with a clinical finish.
Substitute Sergei Rebrov's one contribution to the game was to bundle over Helguson in the penalty box late on.
Helguson scored his 20th goal of the season but it was not enough to prevent Watford slipping to an eighth home defeat of the season and sending West Ham into the play-offs.
West Ham and Ipswich will meet at Upton Park in the first-leg of their semi-final on the weekend of 14 and 15 May.
West Ham were relegated from the Premiership in May 2003.
Watford boss Adrian Boothroyd:
"I don't like to finish the season like that and I would have liked to have finished on a high but we had a go and we will have a go.
"That's the way the team will be set up, to go out and win points.
"If we put in a performance like we did the second-half, we'll certainly win more games than we lose next season."
Watford: Chamberlain, Doyley, DeMerit, Cullip, Chambers, Young, Bangura, Blizzard, McNamee, Bouazza (Osborne 78), Helguson. Subs Not Used: Mayo, Kirk, Mariappa, Grant.
Goals: Helguson 89 pen.
West Ham: Walker, Repka, Ferdinand, Ward, Powell, Newton (Rebrov 83), Reo-Coker (Dailly 90), Mullins, Etherington (Noble 72), Harewood, Zamora. Subs Not Used: Bywater, Fletcher.
Booked: Mullins, Reo-Coker, Ward, Repka, Rebrov.
Goals: Ferdinand 42, Harewood 70 pen.
Ref: A D'Urso (Essex).