BACKGROUND: Seafarers’ psychological health is seriously affected by COVID-19. The pandemic could act as a catalyst for change with respect to seafarers’ mental health protection and promotion. OBJECTIVE: The study explores the main factors contributing to the mental health and wellbeing of seafarers. Moreover, elements to help seafarers lessen the impact of the pandemic on their work and life onboard are analyzed, and their role in developing a positive psychosocial environment and promoting a healthy workplace onboard are discussed. METHODS: The study involved the use of an ad hoc questionnaire and the adoption of both quantitative and qualitative methods. The sample included one hundred and five active seafarers. RESULTS: Ninety-six percent of the sample stated that mental health is a very or extremely important part of their general health. Seafarers perceive that their mental health has been seriously impacted by COVID-19. Major factors contributing to seafarers’ mental health and wellbeing reveal three groups of factors: rest and spare time-related factors, communication/relationship with the external world, and interaction and social life on board factors. CONCLUSIONS: Strategies suggested by seafarers for coping with “inevitable” psychological stress produced by COVID-19 and promoting their wellbeing include managerial, emotional, facilities-related (including communication infrastructure), physical, and social elements to promote wellbeing. Economic, intellectual, and spiritual elements also have to be taken into consideration and require further investigation. Building on seafarers’ insights and experiences, a healthy environment onboard should cultivate holistically the four main spheres of a healthy workplace (physical work environment, psychosocial work environment, personal health resources, and enterprise community involvement) and the five features of a healthy psychosocial environment (social, emotional, physical, intellectual and spiritual) under all circumstances, whether exceptional or ordinary.