It was the Scott-3Rox Racing Team rider's third Olympic participation. He was ninth in the Sydney Olympics in 2000 and the Beijing Olympics in 2008, but sat out the Athens Olympics in 2004 when he was not selected for the team.
"With so many variables in mountain biking, I was happy to be able to produce a solid competitive race in London," said Kabush. "I've always dreamed and prepared to compete for a medal at the Olympics but I have to be satisfied with the best ever Canadian Olympic result in eighth."
Kabush was also the best placed North American rider. Todd Wells, riding for the United States, was the next best in 10th place.
"I owe a huge thanks to the incredible supporting cast behind the scenes as I couldn't do it with this team behind me," said Kabush, who named his team and sponsors specifically.
"I have truly enjoyed the journey to London and if I continue to have as much fun racing as I am now, I might make another run at Rio 2016. Thanks to everyone who has sent messages of support and congratulations."
Kabush's Canadian teammate Max Plaxton also had high hopes for the day after logging his best-ever World Cup finish, on the podium, earlier this summer. But he pulled out of the race after crashing on some gravel and aggravating a knee that had been bothering him for several weeks.