Groom, 29, joins from Super Rugby side Lions and brings a wealth of experience having amassed over 100 appearances for both the Stormers and Northampton Saints in recent seasons.
The scrum-half was a key man in the 2019 Lions Super Rugby squad that narrowly missed out on reaching the knockout stages of the competition, appearing in 13 out of 16 conference fixtures.
On joining the club, Groom said: “I’m really excited to link-up with Edinburgh. I’ve been keeping an eye on their results from South Africa and it’s definitely a club on the rise. I can’t wait to play my role in the seasons to come.
“My time at the Lions has been awesome. I’ve had the chance to work with fantastic coaches alongside some great players and I’m hugely grateful for the opportunity they gave me to play for them.
“From what I’ve heard, Edinburgh is a great place to live and play your rugby. My family can’t wait for the adventure that lies ahead.”
Head Coach Richard Cockerill, added: “Nic is a really intelligent player who has consistently been a standout performer during his time in Super Rugby and the English Premiership.
“That experience in the number nine jersey is obviously key, but Nic’s ability to snipe and create opportunities in and around the fringes brings a different dynamic to our squad, while his addition clearly creates competition for places.
“We’ve been looking at Nic for a while now, so it’s great to finally welcome him to Edinburgh. We’re really hopeful that he can make a strong impact in the seasons to come.”
Born in King William’s Town, SA, Groom attended the University of Cape Town where he lifted the Varsity Cup in 2011.
A double Currie Cup winner with Western Province in 2012 and 2014 – for whom he scored 50 points in 69 appearances – the scrum-half broke into the Stormers’ Super Rugby side in 2014, starting 12 out of 16 games for the Cape Town club.
Groom continued to feature for the Stormers as the Newlands outfit recorded back-to-back third place conference finishes in 2015 and 2016 before joining English Premiership side Northampton Saints at the beginning of the 2016/17 season.
Groom became a regular feature in the Saints’ starting XV and was instrumental in them securing Heineken Champions Cup rugby for the 2017/18 season, appearing in both European play-off games that saw the English side defeat Connacht and Stade Francais to secure their spot in the competition for the following season.
The 5ft 8in playmaker returned to his native South Africa in 2018 – joining the Lions – and featured in eight games as the Johannesburg club reached the Super Rugby final for the third straight season only to fall short against the Crusaders 37-18.
Groom has been capped by South Africa ‘A’, while the scum-half featured for the Barbarians as they defeated Samoa 27-24 at London’s Olympic Stadium in August 2015.