"Tony has been excellent during his loan spell with Sheffield Wednesday and we are grateful for what he has done during his initial spell," Owls boss Brian Laws has said.
"If Boro do not need him in November then we will try to bring Tony back so that he can complete the 93-day loan period he is entitled to serve with us."
McMahon will not be available for selection for this weekend's game against Blackburn as he is suspended for three games following a sending off in Wednesday's defeat against Barnsley on Wednesday night.