The study examined the awareness of adults aged 20–60 years in Isua Joinkrama, Ahoada west local government area, Rivers State, regarding diseases associated with poor oral hygiene. Oral health is a critical component of general health, yet awareness of its impact on systemic diseases remains limited in rural communities. The objectives of the study were to determine the level of awareness of adults about diseases related to poor oral hygiene, identify the oral and systemic diseases perceived to be linked with poor oral hygiene, examine the association between socio-demographic factors and knowledge, and suggest interventions for improving awareness and preventive practices. A descriptive survey research design was adopted. The study population consisted of 1,500 adults in Isua Joinkrama community, from which a sample of 200 respondents was selected using stratified random sampling and simple random sampling techniques. Data were collected using a structured questionnaire divided into socio-demographic items and Likert-scale items assessing knowledge, perceptions, and interventions. The instrument was validated by experts and tested for reliability using a pilot study, yielding a Cronbach’s alpha of 0.82. Data were analyzed using descriptive statistics (frequencies, percentages, mean scores) and chi-square tests to examine associations between socio-demographic factors and awareness levels. The findings revealed that adults had moderate to high awareness of oral diseases such as tooth decay, gum disease, tooth loss, and bad breath, but limited awareness of systemic diseases including diabetes and cardiovascular disease. Education and age were significantly associated with knowledge, while gender was not. Respondents identified community-based education programs, access to affordable dental products, and media campaigns as effective interventions for improving oral hygiene awareness and preventive practices. The study concludes that awareness of oral hygiene is adequate for oral diseases but insufficient for systemic health implications, highlighting the need for targeted health education interventions. It recommends community sensitization, improved access to preventive tools, integration of oral health into primary care, and further research on behavioral practices in rural communities. The findings contribute to public health awareness and provide guidance for policymakers, health educators, and researchers seeking to enhance oral health awareness in rural Nigeria.