The former Sunderland striker struck up a remarkable friendship with the youngster during his time at the club, with Defoe saying walking onto the pitch with Lowery as the highlight of his time at the Stadium of Light.
But since moving to Bournemouth in the summer on a free transfer he clearly deemed it inappropriate to wear either club’s colours.
Defoe joined thousands of mourners in honouring Bradley’s family’s request to wear a football shirt as tributes were paid on Friday.
And as many others have, Defoe’s shirt sports No.6 and Lowery’s name on the back.
Lowery was a mascot on a number of occasions for Sunderland matches, and also famously joined Defoe for England’s match against Lithuania at Wembley in March.
Captain Joe Hart forfeited his right to lead the national team onto the pitch to allow Defoe and his pal Bradley to go out first.
During his short life Lowery saw fans from all clubs come together and thousands turned out to celebrate the impact he had on them.
Fans of Sunderland’s fierce rivals Newcastle also wore his name and No.6 on their shirts in a show of how the young hero touched all in football, not just his favourite club.
Former Sunderland manager David Moyes also paid tribute to Lowery, arriving in a black suit and tie but carrying a Black Cats scarf.
Yorkshire’s cricket team has also announced that its players will wear football shirts during their warm-up for tonight’s T20 Blast match against Lancashire.
A procession through the streets of Blackhall Colliery, County Durham, preceded a ceremony at St Joseph’s Church, with the service broadcast on loud speakers for those unable to fit inside.
Defoe left Bournemouth’s pre-season training camp in Spain to attend the funeral of his little pal.
The forward, who switched clubs in the summer, was devastated when Lowery lost his battle with a rare form of cancer on July 7. He was six.
A private ceremony is being held for family only at a crematorium.
Bournemouth announced yesterday it was giving new signing Defoe compassionate leave to say farewell.
“@IAmJermainDefoe has today departed our pre-season training camp and returned to the UK for the funeral of Bradley Lowery,” the club posted.
Defoe, 34, signed a three-year deal with the Cherries after leaving Sunderland following their relegation from the Premier League.
Eddie Howe’s squad are currently away in Marbella, where they will take on Portuguese side Estoril in a friendly on Saturday.
Bournemouth open the new Premier League season at West Brom on August 12.