A Care Inspectorate report has found that some staff at Kingsmead in Kingswells were not treating people with "dignity and respect".
Some residents had lost weight, with concerns being raised that their nutritional needs were not being met.
The report said that in some incidences, people were being treated like "objects".
The report said one lunchtime service was "chaotic" and the dining experience for people was "very poor".
It said management and staff displayed poor knowledge of clinical needs.
The report called for significant improvements, including staff development.
Mike Best, group managing director of Mead Medical Holdings, said they were concentrating on reducing the number of agency staff, increasing the number of permanent staff and looking at raising standards in the way they operated.
The home can provide care for up to 55 older people, and up to 10 adults with learning disabilities.
The quality of care at an Aberdeen nursing home has been deemed "unsatisfactory".