He has competed in the 800m at two Olympic Games, reaching the semi-finals in Beijing 2008,[7] and finishing fifth in the London 2012 final, running a personal best of 1:42.95 behind David Rudisha's world record of 1:40.91.

Following his retirement, Symmonds gained more popularity in 2020 through his YouTube channel which primarily focuses on running, powerlifting, and fitness.

At Willamette, an NCAA Division III school, Symmonds earned a degree in biochemistry in 2006 and is a member of the Sigma Chi fraternity.

[6] In 2007, he won the 800m race at the Prefontaine Classic meet in Eugene, Oregon, with a then personal best time of 1:44.54, upsetting the current Olympic champion Yuriy Borzakovskiy by beating him with his own come-from-behind strategy.

[18] In 2008, Symmonds won the United States Olympic Trials 800m final held in Eugene, Oregon with a personal best time of 1:44.10.

[20] On June 25, 2012, Symmonds returned to the 2012 United States Olympic Trials again on his home track in Eugene, Oregon.

Symmonds ran around the field and sprinted past Solomon on the homestretch to make his second Olympic team.

[23][24] In January 2016 Run Gum filed an antitrust lawsuit against USA Track and Field for rules that Symmonds felt suppress competition.

[citation needed] In June and July 2020, Symmonds became a topic of controversy in the running community when he organized events ignoring social distancing guidance for his videos.

[33] On November 10, 2023, Symmonds announced via a video on his channel he was taking a break from his YouTube career.

[29] He returned on August 31, 2024 with a video on climbing Denali, the highest peak in North America.

[34] On May 1, 2018, Symmonds announced his official retirement from track & field, along with his next major personal goal; to climb the Seven Summits, the highest mountain on each continent.

[34] At the 2013 World Championships in Athletics in Moscow, Symmonds was a vocal critic of Russia's "anti-gay" laws.

[40] Symmonds published an article in the November 2013 issue of Runner's World magazine advocating that Congress should "ban assault rifles and handguns for everyone except police and military personnel.

[citation needed] Symmonds opposed what he considers absurdly strict rules restricting athletes' ability to market themselves.

[42] Prior to Symmonds, 2004 Olympic champion shot-putter Adam Nelson actively sold space on his shirt during the 2005 season, when he won the IAAF World Championships.

[47] Symmonds has a pet rabbit named Mortimer, with whom he posed for a PETA ad campaign against animal testing.