Due to the close bond Hartson felt with both Celtic Football Club and their fans, he has a tattoo of a large Celtic crest on his upper arm with the words 'You'll Never Walk Alone' underneath in honour of the song which Celtic fans sing ahead of big games. After a picture of the tattoo appeared on the internet and many Celtic F.C. forums, Hartson tweeted that the tattoo was real and in honour of the support he had received from Celtic fans during his illness. The tweet read, "Yes my Celtic tattoo is real I had it done soon as I came out of hospital after the support I was given by the whole Celtic family."