Background Oral frailty can cause many adverse consequences, including by impairing basic oral functions such as chewing and speaking; furthermore, it is closely related to overall systemic health. In the digital age, this study explores the relationship between eHealth literacy and oral frailty, alongside the mediating effects of self-efficacy and oral health on this relationship, providing theoretical support for eHealth-based oral frailty interventions. Methods A multicentre, cross-sectional analysis was conducted from July to November 2024. A total of 636 older adults were recruited from Changning District, Shanghai, China. The eHealth Literacy Scale, the Geriatric Self-Efficacy Scale for Oral Health, the Oral Health Assessment Tool, and the Oral Frailty Index-8 were used to assess the participants' eHealth literacy, self-efficacy, oral health, and oral frailty. Spearman's correlation analysis was conducted to examine the relationships among these variables. A structural equation model was used to analyse the mediating effects. Results The study included 636 participants (55.7% female; median age: 70 years (IQR: 65-75)), whose median Oral Frailty Index-8 score was 5 (IQR: 3-6). Significant correlations were observed among eHealth literacy, self-efficacy, oral health, and oral frailty (P < 0.001). eHealth literacy directly affected oral frailty (beta =- 0.161, 95% CI: -0.233, -0.085) via three mediating pathways: the self-efficacy pathway (beta = -0.147, 95% CI: -0.188, -0.107), the oral health pathway (beta = -0.152, 95% CI: -0.222, -0.100), and the serial mediation pathway via both self-efficacy and oral health (beta = -0.105, 95% CI: -0.136, -0.081), which accounted for 26.0%, 26.9%, and 18.6% of the total effect, respectively. Conclusions eHealth literacy is negatively correlated with oral frailty, in which context self-efficacy and oral health serve as important serial mediating factors. It is essential for health care providers to focus on eHealth literacy among older adults and to support the development of age-friendly oral digital health technologies that require lower levels of eHealth literacy, thus improving the accessibility and equity of digital oral health technologies. This approach may serve as an effective intervention to prevent/delay oral frailty in older adults.