Ibrahim Langoo was left nauseated after spotting a 'wrinkled brain' inside a piece of chicken while tucking into a Gladiator box meal at a branch in Colchester, Essex.
The 19-year-old took a photograph of the three-inch piece of offal - later judged to be a kidney by KFC's experts - on his mobile phone and complained to staff.
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Nauseated: Horrified student Ibrahim Langoo, 19, who found what looked like a lump of brain attached to a piece of chicken in his KFC Gladiator box meal at a branch in Colchester, Essex
Mr Langoo and friend Laura Canning, 19, had popped into the Colchester, Essex branch of the fast food restaurant - known for its 'Finger Lickin' Good' slogan - for lunch between classes.
The pair - both musical theatre students at Colchester Institute - shared a £6.79 Gladiator box meal.
Miss Canning ate the fillet burger, while Mr Langoo went for the two chicken pieces.
'The first piece was absolutely fine - I was hungry and polished it off,' Mr Langoo said.
'I have a habit of picking the chicken off the bone with my fingers, and as I pulled the second piece apart I saw this horrible wrinkled foreign body.
'I threw it down onto my tray immediately. It looked like a brain.
'I suddenly felt grim and really sick.
'I couldn't bring myself to pick the lump up so I went to the serving counter to complain.
'It was about 1pm and pretty hectic in the restaurant and as it was so busy none of the staff helped me.'
Wrinkly: A photo taken by Mr Langoo on his mobile phone of the brain like discovery. KFC experts later said they believed it was a chicken kidney and the company have offered the young man vouchers for more free food
'I didn't want to pick the "brain" up as I couldn't bear to look at it,' Mr Langoo said. 'I was grossed out by the fact that I could so easily have eaten it without realising.
'I just wanted to get out of KFC as quickly as I could. I still feel really sick and disgusted by it all now.
'KFC say they are sorry and are concerned to hear of my experience as they have "rigorous standards" but I'm still not impressed.
'I never want to eat KFC again - in Colchester or anywhere else. I'll eat chicken at home, where I can see how it's been prepared'
Experts at KFC have examined the photograph and believe the unsightly organ was a chicken kidney.
A spokesman for the firm said: 'We always try to ensure the highest standards in all of our restaurants.
'Although we haven't received the product, it appears from a photograph that unfortunately on this occasion a kidney, and not a brain as claimed, was not removed in the preparation process.
'We're very sorry about Mr Langoo's experience and while there was no health risk, we agree it was unsightly.
'We will be carrying out a full investigation and providing him with a gesture of goodwill.'
KFC refused to disclose the amount of vouchers that could be available.