Individuals with disabilities are regarded as a highly vulnerable population group, particularly as far as oral health is concern. However, few studies have assessed the impact of the oral condition on the quality of life of these individuals. Therefore, the aim of this study is to expand knowledge on the oral health status of the Portuguese adults with mild intellectual disability, and to assess how the patient’s oral health is related to their quality of life. A sample of 240 adults with mild intellectual disabilities linked to the Portuguese Federation for Intellectual Disability, were interviewed using a previously validated version of the Oral Health Impact Profile. An oral health examination was also conducted using three oral health indexes: Clinical Oral Health Index (COHI); Clinical Oral Care Needs Index (COCNI) and the Clinical Oral Prevention Index (COPI). Sociodemographic characteristics and dental health factors were also collected, following statistical analysis. More than half of the individuals (54,9%) presented one or more problems of major to severe impact on health (COHI level 2); only 4,6% of the individuals do not need treatment or examination (COCNI level 0) and 85% of the study sample needs measures of educational or preventive action (COPI level 1). In 76,9% of the participants, oral health had impact on the quality of life. The most affected dimensions of life were physical pain with 61,9%, followed by psychological discomfort and psychological disability with 45,1% and 45%, respectively. With relation to oral health factors and sociodemographic variables it was verified that fewer teeth and higher self-perception of need for dental treatment had a negative impact on the quality of life. On the other hand, institutionalization and an increase in at least one category in the self-perception of the oral health status had a positive impact on the quality of life. Given the high burden of oral disease and the considerable impact on quality of life found in this study, the establishment of guidelines to improve the oral health and quality of life of these individuals should be regarded as imperative.