A story was published on the site and forced the six-year-old terminal cancer sufferer's family to deny the cruel rumour.
LADbible came under a storm of criticism, with calls from many to boycott the site as a result of the fake story.
However, the Blackhall youngster's mum Gemma has said that while the incident as upsetting, she has accepted it was a genuine mistake
The organisation issued a full apology on its facebook page, where it pledged its continued support along with the large donation.
The post - titled Bradley Lowery: An apology - stated: "Earlier today we posted an incorrect story about Bradley Lowery, the inspirational young Sunderland supporter whose courageous battle against cancer has captured the hearts and minds of people around the world.
"We realise the magnitude of our error and unreservedly apologise to Bradley and his family.
"We’re now investigating how and why this story was published to our website.
"It should not have been.
"We are in contact with Bradley’s family to discuss this matter further, and have already committed to a £20,000 donation to support his Neuroblastoma treatment.
"Bradley’s fundraising page is: https://www.justgiving.com/crowdfunding/bradleylowerysfight.
"Once again, we cannot even begin to imagine the upset this will have caused Bradley, his family and anybody else following his brave fight.
"Our deepest apologies.
Despite the full apology, the website came under further fire from people commenting on the post, and Gemma personally replied, urging them to see the bigger picture.
She said: "LADbible have supported Bradley a lot and a mistake has been made by one person not the full team.
"We have accepted their apology and would like to move forward from this. Thank you for supporting us guys x"
A statement on Bradley Lowery's fight against neuroblastoma facebook page read: "I have spoken to the lad bible who have apologised for their mistake and would like to support Bradley's foundation moving forward.
"Although seeing the status was very upsetting mistakes happen and we would like to accept the apology and move forward from this.
"The lad bible have always supported Bradley's campaign and this has not changed.
"We have built our campaign on positivity and we would like to continue with this.
"Thank you for everyone's continued support."