Background: Diabetes mellitus is a chronic disease which is becoming increasingly prevalent worldwide. In the Sultanate of Oman, the incidence of diabetes mellitus is ∼15.7% based on national survey in 2017. People with diabetes are at higher risk of oral health problems, including periodontal disease, dental caries and candidiasis; in particular, there appears to be a two-way relationship between periodontitis and blood glucose control. While previous research has indicated that diabetics have poor awareness of oral health, there is a gap in the literature from the Sultanate of Oman. Aim: This study aimed to determine oral health knowledge, attitudes and practices among Omani diabetics. Method: A cross-sectional study was conducted using a convenience sample of 400 adult Omani diabetics who attended the outpatient clinic of the National Diabetes and Endocrine Centre in Muscat, Sultanate of Oman, and who were followed-up for 6 months between May 2019 and May 2020. A self-administered, Arabic-language questionnaire to assess oral health knowledge, attitudes and practices was developed and validated. Mean scores were calculated to determine overall levels of knowledge, attitude and practice. Ethical approval was obtained from the Centre of Studies and Research of the national Ministry of Health. Results: A total of 136 (34.0%) male and 264 (66.0%) female diabetics participated in the study. The mean age was 36.64 ± 12.49 years. The majority (76.8%) of participants demonstrated poor knowledge of oral health, especially with regards to complications like gingivitis (32.4%), dental caries (27.3%), halitosis (27.1%) and gingival abscesses (21.5%). Moreover, most (76.6%) were unaware that oral diseases affected glycated hemoglobin. In terms of practices, more than half (54.8%) routinely brushed their teeth twice a day. However, only 14.6% and 12.6% regularly flossed and used mouth wash, respectively. With regards to attitudes, 42%, 17% and 41% of the participants demonstrated poor, moderate and good attitudes towards oral health, respectively. Smokers more frequently demonstrated poor attitudes compared to non-smokers (6.3% versus 1.6%). Discussion: Various studies conducted elsewhere around the world have similarly shown that diabetics have limited knowledge and awareness of oral health. The lack of knowledge among Omani diabetics of specific oral complications such as gingivitis, dental caries, gingival abscesses and halitosis may be due to a paucity of relevant information from health care professionals. Nevertheless, participants in the current study demonstrated good practices with regards to oral hygiene. Comparable findings have been reported from studies conducted in Saudi Arabia and Nigeria. In contrast, a recent systematic review of 28 studies involving 27,894 people with diabetes indicated that diabetics frequently show poor compliance with oral hygiene behaviors and dental visits. Oral self-care behaviors are imperative to minimize the risk of oral health complications associated with diabetes. Previous research has shown that self-management education is an effective method of reducing the incidence and burden of diabetes-related complications.