The striker, who now plays for AFC Bournemouth, has had the name 'Brad' tattooed on his hand so he can always remember his brave little friend.
Defoe is shown getting the tattoo in a video posted on Twitter by his football club.
Related: Jermain Defoe says he would give up his OBE to have Bradley Lowery back"No matter what happens, I can always look at this and it can pick me up," he said in the video.
"This is an important piece that I've been thinking of getting for a while, of Brad, for obvious reasons - my relationship with him and stuff like that."
He added: "I'm going to add some stars and clouds on it. It means a lot to me."
'I love you so much, rest in peace' - Jermain Defoe's touching tribute to best friend Bradley LoweryDefoe, 36, formed a special bond with tragic young Sunderland fan during his time with the Black Cats, when the club and its players were a big support to Bradley and his family as he was battled neuroblastoma, a rare and debilitating form of cancer.
The much-loved six-year-old, who Sunderland, the North East and the whole nation took to their hearts, died in July last year.
His family set up the Bradley Lowery Foundation to ensure his legacy lives on.