Commenting on the news of his retirement, the 30-year-old said: "It has, of course, come as a big shock for me that I have to retire so suddenly. I'm devastated that I won't play again, but the nature of my injury was very serious and I have to appreciate that I have my health."
The former O2 Ireland Wolfhounds prop damaged a ligament in the upper part of his neck during Connacht's Heineken Cup game away to Saracens in January.
Following two medical consultations, he has been directed to cease contact sport with immediate effect.
He will wear a neck brace continuously for three months to stabilise the damage and rule out the need for surgery.
Brett continued: "It's strange to find myself in this situation but I've had time to get over the initial shock and now I am just really grateful for all the opportunities I've had through rugby.
"I'd like to thank my fiancée Patrice and my family and friends, both here in Ireland and in South Africa, for their constant support..
"My team-mates at Connacht, former and present, are some of the best friends I have and the memories of sharing the highs and lows of professional sport with them is something I'll have forever.
"Being with Connacht for eight years, I've worked under some great coaches and I have to thank Michael Bradley and Eric Elwood for their guidance.
"I've only worked with Pat Lam for one season but I've learnt a hell of a lot from him in that short time and I have to thank him for that.
"But I'd like to particularly thank Dan McFarland, who has coached me since my arrival at Connacht and who influenced my game in so many ways.
"The backroom staff have also been fantastic throughout and especially in the last few weeks when I've been dealing with the news. I'd like to thank our team manager Tim (Allnutt), physio Gavin (Malouf), the doctors and everyone working behind the scenes at Connacht.
"The Connacht supporters are some of the best supporters in the world and I'd like to thank them for welcoming me so openly to Galway and Connacht - a place I now call home.
"My whole rugby career has been with this province and I've witnessed some massive changes but one thing remains and that is the decent people here.
"Connacht has been building and building every year and while I'm sad I won't be a part of it in the same way anymore, I'm excited to follow their progress as a supporter and friend.
"While I haven't had a whole lot of time to think about what to do next, I know that I will be in Ireland. I've been involved in coaching at club level around the province and it's something I've really enjoyed and would like to explore further.
"Outside of rugby I have always had a keen interest in business and while playing I was able to complete a diploma in Sales as well as a certificate in Accounting.
"I would like to look at a degree in Business Management now and hopefully the skills I've picked up through rugby can take me forward into a different sector. I'm excited about what lies ahead."
Dan McFarland, Connacht assistant and forwards coach, said: "Brett has been a tremendous asset to Connacht Rugby over the last eight years.
"It is extremely unfortunate for him and the province that an injury should curtail his career. He arrived as an unheralded but talented club player and managed through hard work and perseverance to deservedly wear the number one jersey for a long time.
"I have really enjoyed working with him, am very sad to see him finish but am certain whatever path he chooses will lead him to success."
Connacht head coach Pat Lam added: "From the moment I arrived here, I was able to recognise Brett as a true 'team man'.
"He is not afraid of hard work and he represents what it is to be a Connacht man and wear the Connacht jersey.
"The work he did this season with Dan and the coaches to improve his game was phenomenal and he has been so reliable for us on and off the pitch. While I am extremely disappointed for him at this time, I am also very relieved that he is fit and healthy beyond rugby.
"I am confident that, with the support of his fiancée Patrice and his family, Brett will go on to succeed in whatever he puts his mind to. For now, he will remain a big part of the squad as we look to finish the season on a high."
Wilkinson joined Connacht in 2006 from the University of Cape Town. Hailing from Grahamstown in the Eastern Cape, South Africa, he began playing rugby from the age of 8.
It was his performances for his school which led to him being singled out for a scholarship to the University of Cape Town.
His first Connacht cap was in 2006 against Borders at Netherdale in Scotland, and Wilkinson went on to earn a reputation at the Sportsground for his powerful scrummaging and excellent ball-carrying skills.
The Irish-qualified prop featured in 17 of Connacht's 23 games this season and wore the Connacht jersey a total of 183 times over eight seasons.
He represented the O2 Ireland Wolfhounds on five occasions and played for Ireland in an uncapped friendly against the Barbarians before embarking on the senior tour to New Zealand in the summer of 2012.
Name: Brett Wilkinson
Date of Birth: November 29, 1983
Birthplace: Grahamstown, South Africa
Height: 1.83m (6ft)
Weight: 117kg (18st 5 lb)
Club: Galwegians RFC
Connacht Caps: 183
Connacht Debut: v Border Reivers, Netherdale, September 1, 2006
Ireland Wolfhounds Caps: 5 (2009-2012) (v England Saxons (x2), Scotland 'A', Tonga XV, Argentina 'A')
Ireland XV Cap: 1 (v Barbarians, May 2012)