Glenview Care Home in Portadown agreed to close after the latest in a series of critical inspection reports.
The Regulatory and Quality Improvement Authority (RQIA) carried out an unannounced inspection on Thursday.
Around the same time, the home's owner, Brendan Breen, applied for voluntary cancellation of its registration.
A series of inspections and follow-up reports dating back to September 2014 had raised many concerns about conditions at the home which currently has about 20 residents.
Those residents will now come under the care of the Southern Health Trust.
In a statement on Friday afternoon, the trust said it would be working closely with the RQIA to ensure a safe transfer of all residents to alternative accommodation.
Among the issues highlighted in the various reports was a lack of "a robust cleaning schedule or supervision to guide the work of domestic assistants".
Concerns were also raised around infection control.
One report concluded that the home was not fit for purpose with the majority of bedrooms not well maintained and in a poor state of repair, beds stained and carpets soiled.
On Friday, the police told the BBC the allegations were being "jointly investigated" by the PSNI's Public Protection Branch and specially trained social workers from Southern Health and Social Care Trust.
They did not give any details of the investigation or the nature of the allegations but added that the "safeguarding of any vulnerable victim is a priority for the PSNI".
The police are carrying out an investigation into allegations relating to a care home in County Armagh which closed on Thursday.