The Demons have been without Brown for the past two weeks after the club decided to ease their premiership forward's workload amid a battling knee issue.
After the absence, Brown is now feeling the best he has for close to three months, shaping up as a key target for Simon Goodwin's side in their push to defend last year's flag.
Speaking to media on Thursday morning, Goodwin confirmed Brown will make his return in Round 21 against the Magpies, along with Harmes, who has been sidelined with concussion.
"He's an important player for us," Goodwin said of Brown.
"You saw what he was able to do at the back end of last year and his form was really trending before he went out of the team with his knee.
"He gives us a real focal point, he's a really smart player, he's a goalkicker and he maximises his opportunities.
"He said this is the best he's felt in probably 12 to 14 weeks, so it was a great opportunity to give him some rest and get him some treatment on that knee, and then just to re-load it a bit in the right way.
"He's feeling 100 per cent and he trained incredibly well the other day."
The former Roo's inclusion will place some selection pressure on fellow forward Sam Weideman, who was limited to just the one possession last week against the Dockers.
Despite his limited influence on the statsheet, Goodwin stressed Weideman's role goes beyond metrics and numbers.
"Obviously, last week wasn't the game he was looking for but he's more than possessions and marks and goals," Goodwin said.
"He competed incredibly strongly for us and he's got a process in place about how he takes his game to the next level."
The Demons will confirm their 22-man lineup to face Collingwood on Thursday evening at 6:20pm (AEDT), with the match to commence at 7:50pm on Friday night.