The 26-year-old arrives in west London after NAC were relegated from the Eredivisie, finishing second from bottom last season.
Kemper began his career with Ajax’s reserve team before spells at ADO Den Haag and NAC, whom he joined in 2023.
He captained Breda to promotion in his first season and spent three years developing into a key figure and leader.
“First of all, I’m excited,” he said. “New club, new city, new competition - I'm looking forward to start and see all the guys.”
“It's a very nice league to play and when you're a little boy, I think everyone is looking to play in a league like this.
“For me, it's also a big challenge to get the club where they belong - a club like this belongs in the highest level.”
QPR, who finished 15th in the Championship last season, will look to his experience and leadership to strengthen their defensive options ahead of the new campaign.