The Royals have already brought in nine new players for their Premier League campaign after winning the Championship title last season.
McDermott believes their transfer business stands up to scrutiny and, while he will not rule out a late move, he suspects there will be no further additions.
"I don't think we'll be doing anything," the 51-year-old told Reading's official website.
"We've signed seven senior players and two younger players which is right up there with everyone in this league. You never say never but I don't think so."
Reading have been linked with England striker Carlton Cole, but McDermott said: "He plays for West Ham, I don't know where that has come from."
Notts County winger Alan Judge is another name who has been mentioned but the managed added: "No, he's a good player we know about but we've got wide players here."
It is more likely that there will be players exiting the Madejski Stadium shortly with Simon Church expected to leave the club on loan.
McDermott said: "It's possible, but that would be a loan so it can go beyond Friday.
"We've got five strikers plus young Dominic Samuel. Robbo (Jason Roberts) is coming back, and there aren't many teams who go with five strikers, I need to give Churchy some games."