Born in Cologne, Frodeno started out as a swimmer in South Africa at the age of 15, and he entered triathlon in 2000.

Frodeno continued to perform strongly in 2009 and 2010, finishing 4th overall in the World Championship Triathlon Series both years.

He was on course to become World Champion in 2010, needing only a 4th place in the Series Grand Final in Budapest, but due to an injury struggled to a 41st-place finish, losing the Overall title to Javier Gómez.

Instead he made his season debut at Ironman 70.3 Oceanside, winning the event while edging out Andy Potts and Lionel Sanders.

[16] He won the 2015 Ironman 70.3 World Championship defeating Sebastian Kienle and the defending champion Javier Gómez.

[17][18] On October 10, 2015, he made history, becoming the first triathlete, male or female, to win both the Olympic Triathlon Gold and the Ironman World Championship title.

[21] He won his second Ironman World Championship in October 2016, pulling away from 2014 champion and countryman Sebastian Kienle early on the run.

With Patrick Lange taking 3rd place, it was the first sweep by a country since 1997, when Germany also managed the feat with Thomas Hellriegel, Jürgen Zäck, and Lothar Leder.

He broke the course record- previously held by Patrick Lange- by 1 minute and 26 seconds, finishing in a time of 7:51:13, becoming the third triathlete to complete the World Championship in under 8 hours.

[24] Frodeno is married to Emma Snowsill, the gold medalist in women's triathlon at the 2008 Summer Olympics.