Self-development behavior introduces auditors as fair judges of the financial world who adhere not only to numbers but also to human and moral values. This balance between technical knowledge and human insight elevates professional judgments from a purely technical level to a deep and influential level. The purpose of this study is to present a model for auditors’ self-development behavior and examine its impact on auditors’ professional judgment. This research is a mixed (qualitative-quantitative) research. In the qualitative part, the content analysis method and interviews with 16 academic experts and auditing professors with professional experience in the field of auditing, as well as members of the Auditing Standards Committee, were used to determine the components of auditors' self-development behavior. Then, in the quantitative part, data on the dimensions of auditors' self-development behavior and their professional judgment were collected for 392 auditors in 1403 using a questionnaire. In addition, structural equation modeling using the partial least squares method (PLS-SEM) was used to test the research hypothesis. The results in the qualitative section indicate 3 overarching themes (professional self-awareness, continuous learning, and responsibility and commitment to the profession), 6 organizing themes (deep understanding of the role of auditors, development of critical insight of auditors, updating of auditors' technical knowledge, development of auditors' soft skills, commitment to auditors' professional ethics, and auditors' accountability to society), and 58 basic themes. The findings of the quantitative section also show that the dimensions of auditors' self-development behavior (including self-awareness, continuous learning, and responsibility) have a positive and significant effect on the quality of professional judgment. The results of this study can be of great help to regulatory bodies, auditing standard setters, and professional institutions in designing professional development and training programs.