The aim of this cross-sectional study was to evaluate the impact of anxiety and quality of sleep on quality of life (QOL) in undergraduate dental students. A total of 141 students were enrolled. All were required to answer the following questionnaires: the State-Trait Anxiety Inventory (STAI) subscale state (S) (STAI-S); the Sleep Assessment Questionnaire (SAQ); and the simplified World Health Organization Quality of Life survey (WHO QOL-bref). The statistical analysis included univariate and bivariate analyses and Poisson regressions. The mean age of the participants was 22.9 (SD=5.2) years; 81.6% were women, and 37.6% studied during the morning shift. The mean STAI-S score was 50.3 (SD=9.4). Sleep problems, classified as "always" or "frequently", were reported by 11.3% and 18.4% of the sample, respectively. Quality of life had a mean score of 13.2 (SD=2.0). The STAI-S and SAQ scores showed a significant association with all WHOQOL-bref dimensions (p<0.05). Analyses performed using multivariate regression and the highest STAI-S score (RR=1.46, 95%CI=1.03-2.06) and SAQ (RR=1.39, 95%CI=1.02-1.90) demonstrated significant sleep problems, even when other variables were controlled to prevent confounding biases. In conclusion, the dental students evaluated showed high levels of anxiety and sleep disorders impacting on QOL.