The 17-year-old had been unable to play for the club since his reported ÂŁ10m move from French side Metz in January, after FIFA blocked his registration under rules restricting the international transfer of players under 18.
Aston Villa confirmed on Tuesday that the Court of Arbitration for Sport, known as CAS, had upheld their appeal, clearing Madjo to play in official competition for the first time since joining. Madjo, who was born in Enfield and holds a UK passport, moved to Luxembourg as a child and represented the country at senior level before switching allegiance to England's youth set-up, complicating his case under FIFA's Article 19 protections for minors.
Without the successful appeal, he would have remained sidelined until his 18th birthday in January 2027. The striker has already shown what Villa have been missing, scoring four goals in pre-season, including two in the club's opening friendly against Walsall.
Madjo's registration news arrived hours after Unai Emery's side picked up a fresh injury concern during Tuesday's 3-1 win over BG Pathum United in Thailand.
Villa captain John McGinn was withdrawn with a suspected knee injury after landing awkwardly following a foul in midfield, having only recently returned from a seven-week absence with a separate knee problem earlier this year. McGinn attempted to continue but was waved off by Emery as a precaution. Chelsea loanee Alejandro Garnacho was also forced off before half-time with a bloodied mouth after a collision with an opponent.
Emi BuendĂa, Victor Lindelöf and Boubacar Kamara were on target as Villa saw out the win, with Kamara marking his return from a lengthy layoff with a goal shortly after coming on. Madjo himself featured off the bench in the second half.
Villa have not yet provided a diagnosis for either injured player, with both to be assessed ahead of Friday's tour finale against Bayern Munich in Hong Kong, a squad already missing several senior players, including Ollie Watkins and Emi Martinez, through international commitments.
With Madjo now free to play a full role following the CAS ruling, Villa have an added attacking option regardless of how the McGinn and Garnacho assessments go. The timing is notable, too, with the teenager set to be available for Villa's Super Cup final against Paris Saint-Germain next Wednesday, having already been used off the bench against Pathum.