Mourners wore Chelsea and Cambridge United colours to celebrate the life of Tommi Miller, who was eight.
Terry met Chelsea fan Tommi last year, and when he was told of the boy's death he volunteered to pay for the service.
Tommi was laid to rest near his Cambridge home in a Chelsea-blue casket bearing the club logo.
Tommi, who was diagnosed with leukaemia aged three, died last month after a bone marrow transplant proved unsuccessful.
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Family friend Tawney Bianca Toogood contacted Terry on Instagram to tell him the boy he had been photographed with had died.
When she explained the family could not afford the funeral they wanted for their son, the former England captain got in touch with the funeral parlour and covered the full Â£1,600 costs.
Tommi's mother Ruth said she was "overwhelmed" by the gesture and "very proud" the footballer - one of her son's favourite players - remembered him.
Most of the arrangements for Tommi's funeral were made by Mrs Toogood's mother Mally Beaver, and sister Chelsea.
The families became friends after meeting on the cancer ward at Addenbrooke's Hospital in Cambridge.
"My father battled leukaemia for just 12 weeks, but Tommi fought it for five years," Mrs Beaver said.
"His family found times tough and we did everything we could to help them out."
When Tommi died the Beaver family, from the travelling community, reached out to other travellers for help.
"Roo and Kevin [Tommi's father] aren't from the community, but everyone took them to their hearts," Mrs Beaver said.
Travellers from as far afield as Canada, Australia, Scotland, Lancaster and Harlow raised more than Â£4,000 to help towards "a celebration of Tommi's life".
As well as the specially-made casket, Mrs Beaver arranged for 100 blue balloons to be released at the service, and had 100 blue roses brought over from Holland "to make it special for him".
The extra money raised will be put towards a headstone for Tommi's grave.
The football-themed funeral of a boy who died from cancer has taken place after Chelsea captain John Terry paid for it.