Introduction: Healthcare workers are vulnerable to adverse mental health impacts of the COVID-19 pandemic. We assessed prevalence of mental disorders and associated factors during the first wave of the pandemic among healthcare professionals in Spain. Methods: All workers in 18 healthcare institutions (6 AACC) in Spain were invited to web -based surveys assessing individual characteristics, COVID-19 infection status and exposure, and mental health status (May 5 - September 7, 2020). We report: probable current mental disorders (Major Depressive Disorder-MDD- [PHQ-8>10], Generalized Anxiety Disorder -GAD- [GAD -7>10], Panic attacks, Posttraumatic Stress Disorder -PTSD- [PCL-5>7]; and Substance Use Disorder -SUD[CAGE-AID>2]. Severe disability assessed by the Sheehan Disability Scale was used to identify probable "disabling" current mental disorders. Results: 9,138 healthcare workers participated. Prevalence of screen -positive disorder: 28.1% MDD; 22.5% GAD, 24.0% Panic; 22.2% PTSD; and 6.2% SUD. Overall 45.7% presented any current and 14.5% any disabling current mental disorder. Workers with pre -pandemic lifetime mental disorders had almost twice the prevalence than those without. Adjusting for all other variables, odds of any disabling mental disorder were: prior lifetime disorders (TUS: OR=5.74; 95%CI 2.5313.03; Mood: OR=3.23; 95%C1:2.27-4.60; Anxiety: OR=3.03; 95%C1:2.53-3.62); age category 1829 years (OR=1.36; 95%C1:1.02-1.82), caring "all of the time" for COVID-19 patients (OR=5.19; 95%C1: 3.61-7.46), female gender (OR=1.58; 95%C1: 1.27-1.96) and having being in quarantine or isolated (OR= 1.60; 95C1:1.31-1.95). Conclusions: One in seven Spanish healthcare workers screened positive for a disabling mental disorder during the first wave of the COVID-19 pandemic. Workers reporting pre -pandemic lifetime mental disorders, those frequently exposed to COVID-19 patients, infected or quarantined/isolated, female workers, and auxiliary nurses should be considered groups in need of mental health monitoring and support. (C) 2020 The Author(s). Published by Elsevier Espana, S.L.U. on behalf of SEP y SEPB.