The present study aimed to identify, structure, and prioritize the factors influencing employer branding and employee mental well-being and to explain the causal relationships among these factors in organizations affiliated with the Social Security Organization. This applied qualitative study employed Interpretive Structural Modeling (ISM) to develop a hierarchical model of influential factors. Participants consisted of experts in human resource management, employer branding, and employee well-being selected through purposive and snowball sampling. Data were collected through extensive literature review and in-depth semi-structured interviews conducted until theoretical saturation was achieved. Extracted factors were analyzed qualitatively, after which expert judgments were used to construct the Structural Self-Interaction Matrix. Initial and final reachability matrices were generated to determine driving power and dependence levels among variables. Subsequently, hierarchical level partitioning and MICMAC analysis were applied to classify variables and validate the structural stability of the proposed model.  Inferential results revealed that the determinants of employer branding and employee mental well-being are organized into seven interrelated dimensions forming a hierarchical system. Individual and organizational development emerged as the most influential driving factor, functioning as the foundational element of the model. Organizational culture and internal communication operated as linkage variables, transferring developmental effects across organizational processes. Job satisfaction together with employee motivation and participation played mediating roles by translating organizational conditions into psychological outcomes. Employee mental well-being was identified as a prerequisite for successful employer branding, while organizational brand represented the final dependent outcome characterized by high dependence and limited driving power. MICMAC analysis demonstrated strong interconnectivity among variables and indicated that systemic changes originating from foundational factors propagate throughout the entire organizational structure. The findings indicate that sustainable employer branding is primarily an internal organizational outcome rather than a purely external promotional construct. Continuous employee development, supportive organizational culture, effective communication systems, and enhanced psychological well-being collectively create the conditions necessary for a strong employer brand. Organizations should therefore adopt a systemic and development-oriented strategy, beginning with investment in employee growth and organizational learning, to foster motivation, job satisfaction, and mental well-being, ultimately strengthening long-term employer brand attractiveness.