Competing nations are allocated a squad of 20 players for the Tournament, but the Three Lions travelled to Provence with just 19 players following the withdrawal of Harry Kane after an injury picked up in the win over Wales last week.
And Gareth Southgate has called upon the 21-year-old to join the squad after his loan spell with Queens Park Rangers came to an end on Saturday.
England v Brazil
The Toulon Tournament
6.30pm, Monday 26 May 2014
Stade Louis Hon, St. Raphael
Live on BT Sport
Keane had been an un-used squad member for Harry Redknapp’s side during their Championship play-off victory over Derby County at Wembley.
He arrived at the England base in southern France on Sunday evening and joins his twin brother and Old Trafford club-mate Michael in the squad for the remaining matches against Brazil, Korea Republic and Colombia.
Head coach Gareth Southgate said: "Originally, anyone that was in the play-offs we left with their clubs, but once Harry was injured we looked at who might be at a club in the play-offs but not necessarily involved.
"We knew we were okay for the first game but it was essential that they were here for this week and I'm really pleased to have Will here.
"He's been with us and trained before, so we know his character and we have a really good group here so he fits right in.
"He's really enthusiastic about coming and playing and that's exactly what we want as it fits in with the mentality of the group."
Keane had worked with Southgate’s team earlier in the season, after recovering from a knee injury sustained whilst on duty with England U19s in May 2012.
The squad will head to St. Raphael on Monday morning to prepare for their second match of the competition against the South Americans later that evening.