<p>This study aimed to evaluate the levels of depression, anxiety, and stress (DAS) experienced by 4th and 5th-year dental interns at Kahramanmaras Sutcu Imam University Faculty of Dentistry, and to investigate the relationship of these psychological conditions with demographic factors. A cross-sectional study was conducted among 126 dental interns during the 2024–2025 academic year. Data were collected using self-administered survey forms, which included basic demographic information, perceived internship challenges, and their mental health status, assessed over the previous week using the Depression Anxiety Stress Scale-21 (DASS-21). The gender distribution of the 126 students in the study was 61.1% female and 38.9% male. Among the students, 55.6% identified dentistry as their first choice. The overall mean DASS-21 scores for the entire sample were Depression: 18.68 ± 11.40, Anxiety: 17.20 ± 10.19, and Stress: 20.40 ± 10.83. The prevalence of extremely severe levels of depression, anxiety, and stress were found to be 29.4%, 39.7%, and 15.9%, respectively. 4th-year students (Depression: 22.20 ± 12.18; Anxiety: 21.21 ± 11.62; Stress: 23.97 ± 12.20) exhibited statistically higher DASS scores across all subscales compared to 5th-year students (Depression: 15.38 ± 10.62; Anxiety: 13.42 ± 8.64; Stress: 17.05 ± 9.37) (<i>p</i> &lt; 0.05). Significant differences were also identified between mental health and sources of financial support, as well as peer relationships (<i>p</i> &lt; 0.05). Positive significant correlations were found between the perceived difficulty levels during the Prosthodontics internship and DASS scores (<i>r</i> = 0.271–0.329, <i>p</i> &lt; 0.05). Identifying effective strategies to support the mental health of dentistry students is critically important not only for safeguarding the well-being of individuals but also for enhancing the overall quality of healthcare services. Therefore, integration of structured psychological support programs into clinical dental curricula is recommended.</p>