Run4Wales said in a statement that the runner had died, adding: "We'd like to acknowledge the event and hospital medical teams who reacted with great speed and professionalism. Our deepest sympathies go out to the runner's family and friends." The organisers said no further details would be released "in respect of the family's wishes".
The Sunday race, Wales' largest mass participation and multi-fundraising event, saw about 30,000 people take to the streets of Cardiff.
The incident is the third time in recent years that the Cardiff Half Marathon has been linked to a runner's death. In 2024, 37-year-old Stephen Jenkins died in hospital after collapsing at the finish line. In 2019, Ben McDonald, 25, and Dean Fletcher, 32, crossed the finish line within minutes of each other, and both died after going into cardiac arrest.