Supervision of counselors-in-training (CITs) is complex and multifaceted. While supervision is critical to the professional development of CITs, they are also being evaluated for a grade that will advance them academically. Therefore, CITs may feel pressured to intentionally withhold information in supervision that could reflect badly on them or their supervisor and/or hinder their progress. Indeed, one study indicated that 97.2% of CITs intentionally withheld relevant information in supervision (Ladany, Hill, Colbert, and Nutt, 1996). Fortunately, there are ways to reduce supervisee non-disclosure. For example, when CITs perceive a strong supervisory relationship, nondisclosures occur less frequently (Mehr, Ladany, and Caskie, 2010). There is some evidence that the supervisory relationship is impacted by the supervisory working alliance and supervisee attachment styles. More general social perceptions may also impact the supervisory relationship, but that has not been assessed in the context of CIT supervision. Therefore, the purpose of this quantitative study was to examine these factors, supervisory working alliance, supervisee attachment styles, and social perceptions, and their impact on intentional nondisclosure by CITs. This quantitative study included a sample of 112 master's-level counselor-in-training students enrolled in internship at a CACREP-accredited (Council for Accreditation of Counseling and Related Education Programs) counselor education program. Results indicate that CITs report more discomfort in disclosing supervision-related issues compared to client-related issues. An exploratory factor analysis of the three constructs of interest resulted in a four-factor model. These factors were: (1) Perception of a Supervisor, (2) Anxious Attachment in Supervision (3) the Supervisory Working Alliance, and (4) Avoidant Attachment in Supervision. A multiple regression analysis indicated that a model including social perceptions of supervisors, the supervisory working alliance, and supervisee attachment styles explained 64% of the variance in intentional nondisclosure. Avoidant attachment styles and rapport of the supervisory working alliance were significant predictors of intentional nondisclosure. Implications for counselors and counselor educators are included. Limitations and recommendations for future studies will be discussed based on the unique findings from this study.