The Bru Aimsir Hostel was set up over the winter
The Peter McVerry Trust is calling for a transition plan to be put in place to prevent 100 people from finding themselves back on the streets.
The Bru Aimsir Hostel in Dublin, which was set up over the winter months to provide emergency beds for homeless people, is due to close in coming days.
The charity is calling for an extension of the closure of the 100-bed facility.
The Trust says it would hope to see a meeting "involving all the partners involved in the Bru Aimsir service, to discuss an extension of the service for a period of weeks".
It says that any sudden withdrawal of bed capacity will negatively impact on vulnerable service users.
"A short extension of the service would prevent this and provide the space for the partners involved in Bru Aimsir and the broader sector to agree a programme to replace these very important beds", it adds.
Separately, the Trust says it is confident of securing capacity to replace the St John's Lane West Hostel in the city - which is scheduled to be turned into social housing units.
Peter McVerry Trust CEO, Pat Doyle, says it is important alternatives are provided.