Introduction: Evidence has accumulated indicating that lung cancer patients have represented a vulnerable population throughout the COVID-19 pandemic. Limited information is available in Latin America regarding the overall detrimental effects of depression, anxiety, and distress due to the ongoing pandemic. This study aimed to determine the prevalence and impact of psychol. disorders due to the COVID-19 pandemic in the medical attention and survival of patients with thoracic cancers. Methods: To determine the impact of COVID-19 in the mental health of thoracic cancer patients, specialized psychiatrists and psych-oncologists performed a cross-sectional mental health evaluation in a single center between March 1st, 2020, to Feb. 28th, 2021. For this purpose, models were developed to test the association between mental health status and delays in medical care, and a second model to test the association between delays in care and survival effects. A logistic regression model was built with binary variables describing timeliness in treatment during the COVID-19 pandemic and the DASS-21 dichotomous explanatory self-reported anxiety, depression, and stress subscales. Scientific and bioethical committees of the Instituto Nacional de Cancerología (INCan) approved this study (020/043/ICI) (CEI/1493/20). Results: Five hundred and forty-eight patients were eligible for the anal. The mean age was 61.5 ± 12.9 years, non-small cell lung cancer (NSCLC) was the most seen neoplasm (86.9%), advanced stages predominated (80%), and the majority of patients were under active therapy (82.8%). The mean DASS-21 score was 10.45, being women more affected than men (11.41 vs. 9.08, p<0.001) in the overall scale and on each subscale (p<0.001). Anxiety was reported in 30.5% of cases, followed by depression and distress in equal proportions (18%). Any change in treatment was reported in 23.9% of patients, of whom 78.6%% were due to the COVID-19 pandemic. Delays (7 days) were the most frequent treatment change in 41.9%, followed by treatment suspension at 37.4%. After adjusting for age and sex, patients with thoracic neoplasms and depression had 4,5 higher odds of experiencing delays on treatment (95% CI 1.53 to 13.23, p1/4 0.006). Similarly, patients with stress had 3,18 higher odds of experiencing delays (95% CI 1.0 to 10.06, p1/4 0.006). Anxiety was not associated with delays in care. Moreover, patients without changes in its cancer treatment had a more prolonged progression-free survival and overall survival, [HR 0.21, p<0.001] and [HR 0.28, p<0.001]. Conclusion: There is enough evidence to suggest that depression among patients with thoracic neoplasms is associated with treatment delays. Changes in primary treatment, especially delays due to pandemic, were associated with lower survival rates than those without changes.