Leaders at St Alkmund's Church say it has become a "focal point for antisocial behaviour".
They revealed there have been a number of complaints and added those that congregate at the church create a bad impression for tourists.
Plans have been submitted to Shropshire Council.
Andrew Cross, treasurer of St Alkmund's Parochial Church Council, said: "Over the past few years the north east porch, a covered porch area outside the north east door, has become a focal point for antisocial behaviour.
"There are rough sleepers, drink and drug taking and dealing, human excrement, litter, needles and noise."
Mr Cross said the action had been agreed following talks with Shrewsbury Town Council, Shropshire County Council and residents.
He added: "It was agreed that significant reduction of these antisocial activities might be achieved by the re-installation of railings, incorporating a lockable gate around the porch area. The gate is necessary to preserve the north east door as an emergency exit during events in the church.
"For whatever reason the police and the councils are having difficulty in controlling the antisocial behaviour in this area and the application is made in effect at the request of the Shropshire Council and Shrewsbury Town Council the police and local residents.
"In 2008 the council did erect a CCTV mast and camera on the church site but this does not cover the North East Porch area.
"St Alkmund's PCC is conscious that the application site is in the town centre and in an area visited by many tourists. The increase in rough sleepers and antisocial activities do not present a welcome sight for visitors and local residents and can be intimidating. The PCC is making this application and is intending to carry out the proposed works at its own expense."
The railings would be re-introduced where "stubs" of the old railings are still visible.