They say it is unacceptable that the Post Office is flying in the face of public demand.
The protest, organised by the Alliance for Green Socialism, was held yesterday outside Chapeltown Post Office in Newton Grove, Chapeltown Road.
It is due to close on April 20 and campaigners say that will leave many residents, including the elderly, without a much needed facility.
One protester, Mike Davies, who lives within a few hundred yards of the facility, said: "This is a very significant closure. It is very well used by locals. Not only is it the only accessible postal counter, it provides the only banking service in Chapeltown.
'Sham'
"How can the council and Government talk about joined up thinking for deprived areas and then close a key service like the local post office?"
He said they had decided to stage a protest after the Post Office announced more closures this year and next.
Mr Davies added: "The Post Office claims the closures are based on a careful survey of the local area and the alternatives.
"These so called "consultations" are a sham. The consultation period was done over Christmas and New Year, deliberately designed to stop people commenting.
"In our experience, the public response has been overwhelmingly against closure but this has been ignored."
He said it was upsetting that many thousands of post offices around Britain were being closed when they provided a much needed facility.
A spokesman for the Post Office said: "Newton Grove Post Office is to close on April 20. After a public consultation the results showed it was not viable and we have agreed with the post master that it will close."
alison.bellamy@ypn.co.u