Stojan Jankovic, known as Stoly, is currently being held in a detention centre in Dorset and could be forced to leave the country as early as Tuesday.
The 52-year-old moved to London from the former Yugoslavia in 1991 and has worked at Earth Natural Foods in Kentish Town Road for the last 15 years.
He was taken into custody “without warning” when he attended his monthly appointment at an immigration reporting centre on Thursday, John Grayson, who co-owns the shop, said.
He told the Standard: “He has been signing on at these appointments every month without fail for the last 10 years.
“Then on Thursday afternoon we got a panicked phone call from him.
“He said ‘they are taking me away’.”
Mr Grayson said Mr Jankovic was put into the back of van before being whisked off.
He added: “He’s reliable, he’s never had a day off work in the time he’s been working for me.
“He has always paid his taxes and his national insurance. He’s never claimed a penny of state benefits.
“Avuncular is the word a lot people use to describe him, He’s cheerful, slightly eccentric, very popular.
“He’s peace loving and leads a quiet life.
“He’s known as our public face, he's very well known in the local community and has been in the country unbroken for the last 26 years.”
Local MP Keir Starmer has asked for Mr Jankovic’s deportation date to be delayed by at least 14 days to allow time for a legal challenge, Mr Grayson said.
Mr Janokvic is understood to have applied for asylum when he arrived in the country but his application was refused.
It is believed his leave to remain in the country expired in 1999 but he has been working and paying taxes since then without any problems.
Mr Grayson added: “Considering the circumstances he’s in good spirits, he understands what’s happening and he’s an optimistic person.”
An online petition calling for Mr Jankovic to remain in the UK was set up on Friday and has already received over 700 signatures, while the hashtag #savestoly has been started on Twitter.
Mr Jankovic is currently at a The Verne Immigration Removal Centre – a former prison in the Isle of Portland, Dorset.
The Home Office has been approached for a comment.