In June 2013, severe flooding struck the departments of Hautes-Pyrénées (65) and Haute-Garonne (31), causing significant disruption and extensive property damage. Since this type of natural disaster is known to affect the mental health of the affected population in the short, medium, and long term, a study of the psychological impact of this event was conducted. It focused on two approaches: for the medium- and long-term effects, a prospective population-based cohort survey using self-administered questionnaires was conducted four and 16 months after the event. It included residents of four municipalities affected to varying degrees by the floods; for short-term effects, a time-series study was conducted to assess psychological disorders three weeks after the floods, based on the dispensing of psychotropic medications in the medical-administrative databases of the National Inter-Regime Health Insurance System (Sniiram). No significant immediate impact on the dispensing of psychotropic medications following the floods was noted. However, the results of the cohort study indicate the existence of a psychological impact (post-traumatic stress symptoms, depression), exacerbated by financial difficulties. The conclusions of these studies highlight the importance of considering the impact of floods on mental health. Recommendations include better targeting, in the days following the floods, the populations most at risk of experiencing short- and medium-term impacts—particularly those who have suffered significant property damage—in order to provide them with appropriate care.