The Tottenham Hotspur midfielder was selected by Gareth Southgate for the upcoming World Cup qualifiers with Slovenia and Lithuania before Three Lions boss knew if Alli would be eligible to play.
He has now learned his fate, and will miss the Slovenia game, and must also pay a fine of £3,852, imposed by Fifa.
The football governing body deemed the incident during the World Cup qualifier against Slovakia in September as “offensive and unsporting”.
Alli maintains that the gesture was aimed at his former Spurs teammate Walker, as an inside joke between the pair.
Fifa’s statement read: “Although the disciplinary committee was not convinced that the player directed the gesture at the referee, and regardless of whether it was allegedly directed at a team-mate, it did consider such gesture to be offensive and unsporting. Therefore it amounted to a violation of article 57 of the Fifa disciplinary code.”