Information regarding individual needs of older adults with intellectual disabilities (IDs) is scarce although it is very important both from a person-centered planning perspective and from a proactive service system perspective. This study has three main aims:(1) to identify and describe staff perceptions of the needs of a large group of adults aged 45 or over with IDs; (2) to analyze the perceived needs as function of age, gender, and level of disability;(3) to present information about the development and the psychometric properties of the assessment instrument used. The participants were 232 Portuguese older adults with IDs (mean age = 52), predominantly male (n = 129). There were 66 staff members who assessed the needs of the IDs participants through the Inventory of Identification of Needs (IIN). The IIN demonstrated satisfactory psychometric properties (e.g., internal consistency, interrater reliability, construct validity). The unmet needs were numerous and diverse, but those that were perceived as more prevalent were: literacy, handling of money, information on rights, self-care, information on services, communication, occupation at holidays, occupation at weekends, general physical health, cognitive rehabilitation, and daytime activities. The needs were influenced by the disability level: regarding Literacy/Information and Occupation/Community, needs were significantly more common in persons with a moderate and/or severe disability. The influence of age was registered only in Mental Health. The needs identified should guide the planning and development of service provision. These should offer literacy learning experiences, information about the rights of persons with disabilities, information about the services available, self-care assistance or training in self-care skills; and meaningful activities during regular time periods, weekends and holidays.