Hoyland has agreed a one-year deal, van der Merwe has signed on for another two years and Kinghorn has extended his stay with Edinburgh until 2021.
The back-three trio have scored 15 tries between them in all competitions so far this campaign.
Edinburgh head coach Richard Cockerill described the new deals as a “huge boost” for the club, adding: “It’s great news that all three players have chosen to stay in Edinburgh.
“Blair has been one of our most dangerous players this season and was fully deserving of his call up to the Scotland squad for the Six Nations – and he’s only continuing to develop.
“Duhan – since returning from injury – and Damien have already demonstrated throughout the season that they’re potent finishers and they’re both central to our plans moving forward.”
• READ MORE - Ulster coach praises ‘scary’ Richard Cockerill’s impact at Edinburgh
Kinghorn, 21, has made 59 appearances in an Edinburgh jersey, currently tops the Pro14 charts for metres gained and defenders beaten, and can boast eight tries this season.
He said: “I’m really excited to be staying at Edinburgh for the next three years. We’ve got a great group of players and coaches and we’re building something special.”
Local boy Hoyland is also closing in on 60 appearances for Edinburgh since joining from Melrose in 2014. He made his Scotland debut against Italy during the 2015 Summer Test series, and has crossed for three tries this season.
The 24-year-old said he was “excited to be at a club that’s constantly moving forward,” adding: “It’s also another great opportunity to further improve as a player and I’m more determined than ever to do so.”
South African wing van der Merwe joined the club last summer from Montpellier, and scored his fourth try of the season during last Friday’s 29-24 victory over Leinster.
The former South Afirca Under-20 cap said: “Re-signing with Edinburgh is providing me with a brilliant opportunity.
“I am really excited to be part of this era of Edinburgh Rugby, and to be part of this fantastic time of growth and success for the club.”
Edinburgh face Ulster at the Kingspan Stadium on Friday night in the Pro14.
• READ MORE - Edinburgh skipper’s rallying call ahead of summer overhaul