The Reds captain sent his condolences after Connor Brown, 18, was killed and made the contribution to a fundraising page.
Two men have been remanded in custody after appearing in court charged with Connor’s murder.
Ally Gordon, 19, and Leighton Barrass, 20, both of Sunderland, appeared in front of South Tyneside magistrates.
Connor, a GP’s receptionist and local boxer, had been on a night out with friends when he was found with stab injuries behind The Borough pub in Sunderland city centre, around 1.30am on Sunday.
Northumbria Police said he was taken to hospital but died a short while later.
Henderson and Mr Brown both went to Farringdon Community Sports College.
The Reds star wrote on the Connor Brown gofundme page: “All our thoughts are with the family and friends of Connor at this heartbreaking time. RIP Connor.”
Now over £18,000 has been raised with the initial target of £8,000.
The fundraising page was set up by family friend Tracey Robinson who described the Brown family as not having a “bad word, bone or hair amongst them.”
She wrote: “Connor was a beautiful, young 18 year old boy with his life ahead of him.”
Ms Robinson continued: “I have known this family on a personal level for approximately 20 years this family does not have one single bad word, bone or hair amongst them.
“They honestly and sincerely are the most loveliest family you could wish to call friends.
“Please, please help me take away the financial pressure that will creep up so quickly, to give this family some relief in the knowing that Connor…a son, brother, grandson and nephew along with a friend to many.”