The funeral is being held for a Sully man who died after he completed a half marathon.
Kory Russell collapsed at the finish line of the the Royal Parks event in London's Hyde Park last month.
The 25 year-old was treated at the scene by paramedics and taken to hospital where he later died - the cause of his death remains unknown.
Ahead of his funeral at Llandaff Cathedral on Friday, Mr Russell was described by his family as "the best son and brother anyone could ask for".
His parents, Matt and Rhi, told BBC Wales: "He'll be remembered for his kindness, his caring nature, his wit, but more importantly, and more than anything, his infectious smile, it would light up a room."
"More often than not he would be smiling at every opportunity. I think that's what we would like him to be remembered for most."
Mr Russell had previously worked as a chef at the Home restaurant in Penarth before he moved to London to join an investment firm.
Paying a personal tribute on Instagram, owner James Sommerin said: "You were a very talented cook, we always said to you, if you changed your mind about a career in finance that there would always be a job for you with us."
"You always stayed in touch with us and always visited when you were home. We always classed you as part of our little family."
"We feel so privileged to have known you and been a part of your life which we know you lived to the full. Our hearts are aching, as many others will be. You will have a special place in our hearts forever."
Mr Russell was also a former member of the City of Cardiff Swimming Club along with his sister, Seren.
Paying tribute on Facebook last month, a club spokesperson said: "Kory brought a warm smile to every session, and his politeness, respect, and positive spirit left a lasting impression. He was an absolute pleasure to coach and a remarkable young man."
A spokesperson for the Royal Parks Half Marathon said: "Everyone involved in the organisation of the Royal Parks Half Marathon would like to express sincere condolences to Kory’s family and friends."
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