Objective:To systematically review evidence on dysfunctional psychological responses of Intensive Care Units nurses (ICUNs), with focus on anxiety and depressive symptoms and related factors. Method: A literature search was performed in CINAHL, PubMed and Scopus databases, from 1999 to present, along with a critical appraisal and synthesis of all relevant data. The following key words, separately and in combination, were used: "mental status" "depressive symptoms" "anxiety" "ICU nurses" "PTSD" "burnout" "compassion fatigue" "psychological distress". Results: Thirteen quantitative studies in English and Greek were included. The results suggested increased psychological burden in ICUNs compared to other nursing specialties, as well as to the general population. Conclusions: Studies investigating psychological responses of ICUNs are limited, internationally. Future longitudinal and intervention studies will contribute to a better understanding of the phenomenon.