It was not just the players and coaches from his former clubs Parramatta Eels and Cronulla Sharks who paid their respects to Mannah, but also opponents who were inspired by his strength of character.

"It's given me a different outlook on life," Wests Tigers Braith Anasta said. "I'm glad I'm here because I'm a better person for it. Anyone who went through what he did is inspirational."

His former Sharks teammate, Ben Pomeroy, struggled for words to describe the generosity and nature of Mannah and says he will be sorely missed.

"He was just a great guy. He would anything for you and we'd do anything for him. I don't know what to say," Pomeroy said.

Mannah, 23, lost his long battle with cancer on Friday morning. His brother Tim, who plays for Parramatta and has represented NSW in the State of Origin arena, has called on mourners to celebrate Jon's life rather than dwell on the tragedy of his untimely passing.

Wests Tigers captain Robbie Farah attended the funeral service and says Mannah's courage through adversity left a lasting legacy on the sport.

"I think everyone knows what kind of person Johnny was and he will be sorely missed. He had a great impact on many peoples lives and it showed with the turn-out here," he said.