Inspectors graded Nethanvale Care Home in Lesmahagow, South Lanarkshire, "weak" for the quality of care and support provided to residents.
The Care Inspectorate report findings also covered the Lower Johnshill building at the site. The two care home buildings are run by Methodist Homes (MHA).
Further attention was required to personal plans, particularly regarding nutrition and wound management, inspectors found.
But the report also revealed residents and relatives spoken to said they were "very happy" with the care and support provided by staff.
Inspectors said March's visit was the second consecutive inspection that found the quality of care and support provided to be 'weak' - the second lowest possible grade.
A Care Inspectorate spokesman said: "We continue to have concerns about the quality of care provided to residents, and we are working with the service to ensure that they improve quickly.
"If we do not see significant evidence of improvement we will not hesitate to take further action."
A spokeswoman for MHA said: "We take this report extremely seriously.
".We are confident that all requirements will be met by the end of June to bring Nethanvale in line with the high standards usually associated with MHA."