Background: The terror attack of July 14, 2016, in Nice, France, resulted in 86 deaths, including children, and several hundred wounded, with a major psychological impact on the population. Hospital staff had to cope with exceptional circumstances which made them vulnerable to detrimental effects on their own health. This paper describes the method that was selected for the survey entitled “ECHOS de Nice 14 Juillet” which aimed to assess the impact of the attack on the psychological, psycho-traumatic and somatic health condition of the Nice University and Lenval hospital staff who were directly or indirectly exposed to the attack, and also to describe the support and care facilities they were offered. Method: ECHOS de Nice 14 juillet is an observational, cross-sectional, multicentre study focusing on all the hospital staff and students of both institutions, i.e. 10,100 persons in June 2017. A web-based questionnaire based on the model developed by Santé Publique France (IMPACTS and ESPA 13 novembre 2015) was adapted to the contexts of the healthcare professionals and students employed in these healthcare institutions in Nice and published on line from June 21 to October 30, 2017. The paper describes the tools that were used to meet the aims of the study, i.e. identification of exposure categories (‘civilian’ exposure for those present during the attack and/or ‘professional’ exposure); indicators of psychological impact (anxiety, depression, burnout, compassion fatigue, suicidal states, tobacco and alcohol use, self-medications), psycho-traumatic and somatic impact; professional and social impact. Lastly, awareness of availability and use of psychological support and care-follow-up facilities by professionals were investigated. Respondents could include extensive qualitative comments on the various themes explored in the questionnaire, with text analysis complementing that of quantitative data. Discussion: The benefits and limitations of the selected methodology are discussed, in view of contributing useful information to help anticipate and manage health issues among hospital staff who have been victims of traumatic events.