Ismaila Sarr’s penalty early in the first half proved to be just enough to earn Watford a 1-0 victory over Millwall and confirm an instant return to the Premier League.
Watford holds off Milwall to secure promotion.
Brentford’s win at Bournemouth earlier in the day meant that only three points would be good enough for Xisco Munoz’s Hornets to be promoted alongside Norwich, who came down with them last season.
Millwall came close on several occasions to delaying a promotion party that traditionally sees Hornets fans jump in a town-centre pond, but Watford hung on.
The Hornets have gathered 88 points from 44 matches so far – five points behind leaders Norwich City with two games remaining and 10 points behind third-placed Brentford.
Sarr is currently the Hornet’s leading top scorer with 13 goals and four assists after 39 Championship matches.
Nigeria defender Troost-Ekong also played a vital role in the Hornets’ successful campaign in the second-tier division with his defensive contributions in 32 appearances.