This study sought to examine Turkish first-time supervisees' opinions regarding disclosure and nondisclosure in clinical supervision via a case study design. The data was collected from 19 volunteer first-time supervisees through a semi-structured interview form and analyzed with content analysis. Results indicated that supervisees' content of disclosures included supervisory needs and thoughts about supervisor while content of nondisclosure consisted of personal issues, supervision-related issues, and negative feelings about client. Nevertheless, supervisee disclosure was positively influenced by supervisor's personal characteristics and interventions; supervisee's expectations from disclosure and personal characteristics, as well as existence of peers in supervision environment and strong supervisory relationship. However, supervisor's personal characteristics; supervisee's personal characteristics, negative attitudes toward disclosure, and supervision; and also peers, poor supervision time, poor structure for supervision, evaluation concerns, and weak supervisory relationship have some negative effects on supervisee disclosure. Moreover, supervisee disclosure and nondisclosure had intense effects on supervisee and supervision.