BACKGROUND: Health literacy involves the use of acquired health information in taking appropriate steps to improve health status and quality of life. It has a strong association with oral health and is a determinant of overall health. This study explored oral health literacy and determined the efficacy of a home-grown intervention program on health literacy and well-being in older adults in Lagos state, Nigeria. METHODS: A multi-stage and multi-phased mixed-method study was conducted among adults ≥50 years with a Charlson comorbidity index score ≤ 1. Phase 1 involved a multi-stage sampling in selecting 6 LGAs from ten LGAs within 10kms radius of Lagos University Teaching Hospital. Two wards were randomly selected from each of the 6 LGAs. Participants from visited households were administered the original version (Cronbach’s alpha = 0.67, confidence interval CI = 0.50 to 0.80) and the Yoruba cross-culturally adapted (Cronbach’s alpha = 0.74) adapted 14-item oral health literacy questionnaire (HeLD 14 - item). Each item of the HeLD 14-item scored 0.5 for Yes responses and 0 for No responses. A maximum score < 4 was considered as low oral health literacy. Phase 2 involved random allocation of participants with low oral health literacy into three groups- 2 interventional groups (Health Belief & Motivation Interview) and one control group. Assessment of interventions was made by determining the proportion of participants taking action (trigger) to have dental assessment and treatment. Phase 3 was a Focus Group Discussion (FGD) of twenty participants selected from the three randomly allocated groups participating in a 40-minute focus group discussion on oral literacy and oral health for thematic analysis. Data was analyzed using Pearson Correlation Coefficient Chi-Square, and the Analysis and level of significance were set at ≤ 0.05. DISCUSSION: A total of 481 respondents. Females made up 67.8% of them. The mean age was 68.91 ± 8.36, with most (45.5%) of them in the 61 to 70 years age group. The majority (45.5%) of the participants were between 61 years and 70 years. There was poor oral health literacy among community-dwelling older adults in Lagos State, Nigeria. The home-grown intervention program based on the health belief theoretical framework is an effective approach to improving oral health literacy in older adults. TRIAL REGISTRATION: This was retrospectively registered at the Pan African Clinical Trial Registry (www.pactr.samrc.ac.za) on the 16th of August 2024. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12903-025-06464-7.