Although men have a higher risk of developing a mental disorder during the perinatal period, few studies have focused on new fathers' mental health screening. This study compares anxiety and depression symptoms between fathers with newborn infants in the neonatal intensive care unit (NICU) and fathers of healthy full-term infants, assessing the impact of stress caused by the NICU.. A longitudinal and prospective study with control (n= 33) and study groups (n=51) was designed. The dependent variables assessed were post-natal depression and anxiety-state while the social and demographic information, health background and the parental stress in the neonatal unit were the independent variables. The fathers were assessed twice during the first month after birth. Significant differences in the EPDS scores were found between both groups in the first assessment (p = .006) but not in the second assessment (p = .60). Significant differences in STAI scores were found between the groups for both assessments (p = .003 and p = .002). The stress caused by the infant's appearance and behavior was predictive of depression and anxiety in the study group. The sample was collected at one hospital, immigrants were underrepresented, and no prenatal assessment of paternal mental health is available. Our results suggest that the hospitalization of newborn infants increases the risk of developing anxiety or depression disorder in fathers. Health providers should be aware of the emotional changes in men shortly after childbirth and include them in the screening of and support for mental health disorders. Copyright © 2020 Elsevier B.V. All rights reserved.