Abdulkadir Mahamoud, 29, was last seen on Friday, 24 February after leaving his home in Easton.
Avon and Somerset Police have said his disappearance is out of character and they are concerned about his welfare.
A social media post written by police about his disappearance was retweeted by the Harry Potter author, JK Rowling on Sunday evening.
Mr Mahamoud was last seen wearing a grey polo shirt and a gold-coloured macawis, which is similar to a sarong and is traditionally worn by Somalian men.
Concerns are growing over the disappearance of a Bristol man who has been missing for over a week.