Watson will become the forward-line coach with Brett Allison accepting a position at Melbourne while Drummond, who joined the club in 2012 as a development coach, will step up and assume responsibility for the defenders.
A former Magpie, Watson began with the Kangaroos in 2010 and has been in charge of the back-line while also helping to develop the likes of Scott Thompson, Shaun Atley and Aaron Mullett.
Meanwhile former vice-captain and defender at Brisbane, Drummond has worked closely with the Kangaroos' VFL representatives at North Ballarat for the past year.
"Josh has been a fantastic addition to our coaching group in the short time he's been here," GM Football Operations Jon Haines told NMFC.com.au.
"He has gained great respect from the players and his playing experience as a defender means he'll continue to bring a wealth of knowledge to the group.
"We feel these changes will be instrumental and very positive and we'll also be looking to make further announcements in the coming weeks."
