To examine chain mediating roles of social support and self-efficacy between quality of frailty and depression in elderly people after percutaneous coronary intervention (PCI). Frailty is a cause of depression among elderly patients after PCI. Although previous studies have shown that frailty, social support, self-efficacy and depression are significantly related, the interaction mechanism remains unclear. Employing a cross-sectional research design and convenience sampling methodology, data were collected at a tertiary hospital in China. Participants completed the FRAIL Scale, Social Support Rate Scale, General Self-Efficacy Scale and the Hospital Anxiety and Depression Scale. We utilised the PROCESS macro in SPSS to ascertain the mediating roles of social support and self-efficacy between frailty and depression. The study used the STROBE checklist for reporting. A total of 241 elderly patients were included in the study, with an average age of 68.05 (6.04) years. Among them, 63.1% of the participants had experienced depression. Elderly patients after PCI's frailty score was negatively correlated with social support and self-efficacy, and positively correlated with depression. Social support was significantly positively correlated with self-efficacy, significantly negatively correlated with depression. Finally, self-efficacy was significantly negatively correlated with depression. Social support and self-efficacy mediated 11.61% and 29.46% of the total depressive role in elderly after frailty and PCI, respectively. Frailty in elderly PCI patients is directly associated with depression and indirectly related through social support or self-efficacy. To enhance the quality of life for elderly patients following PCI, healthcare providers should address the impact of frailty on depression and develop intervention strategies based on the levels of social support and self-efficacy. Questionnaires filled out by patients were used to understand the relationship between frailty, social support, self-efficacy and depression.