Boro's official website confirmed the Egyptian striker's comeback, but mentioned that he didn't catch up with his teammates at the camp as he would undergo a rehabilitation program first.
The Middlesbrough players who took part in the preparations from the beginning went through the same program, and now Mido has to train separately to make up for his absence.
"Mido returned yesterday (Monday) and has been disciplined by the club," first team coach Steve Agnew said.
"He's back with us now, but not yet part of the group as he's now following the program the other players have gone through over the last 10 days or so.
"He's follow that program until he's on a laevel with the others, but that won't happen for a few more days at least because he was late he has to catch-up on everything, including the fitness testing."
Mido was fined by Middlesbrough for not reporting back in time, and was vilified for his lack of commitment.
The 26-year-old has been seeking move away from the Riverside since Boro were relegated the Championship last season.