The 20-year-old has seen off competition from Arsenal pair Hector Bellerin and Alex Iwobi, Fulham's Ryan Sessegnon and former Charlton youngster Ademola Lookman, who joined Everton in January, to claim the award.
Sunday's goal in Tottenham's 4-0 win over Stoke City for All's 12th in the Premier League this season, with the midfielder adding a further two assists.
Alli picked up the same award last year, again beating Bellerin and Lookman, while also besting Fulham's Moussa Dembele, now at Celtic, and Spurs team-mate Eric Dier.
In 12 months, the former MK Dons star has established himself as a regular England international, making 11 appearances and scoring his first competitive goal in a World Cup qualifier against Malta.
Alli was named PFA Young Player of the Year for his stellar breakout season at White Hart Lane, which also earned him a place in the PFA Team of the Year.
In January 2017, Alli was named Premier League Player of the Month for the first time after a scoring run of five goals in five games which included a match-winning brace against Chelsea.
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