Objectives Duration at sea was investigated as a potential chronic stressor amongst seafarers in addition to the mediating roles of previous seafaring experience and hardiness between duration and stress. Methods In a cross-sectional design, questionnaires were emailed to 53 tanker vessels in an international shipping company with questions relating to duration at sea, perceived stress, personality hardiness and work characteristics. The sample comprised 387 seafarers (98 % male) including ratings, crew, officers, engineers, and catering staff that had been on board their ship between 0 and 24 weeks. Results Duration at sea was unrelated to self-reported perceived stress, even after controlling for previous seafaring experience and hardiness. Additional regression analyses demonstrated that self-reported higher levels of resilience, longer seafaring experience and greater instrumental work support were significantly associated with lower levels of self-reported stress at sea. Conclusions These results imply that at least for the first 24 weeks at sea, exposure to the seafaring environment did not act as a chronic stressor. The confined environment of a ship presents particular opportunities to introduce resilience and work support programmes to help seafarers manage and reduce stress, and to enhance their well-being at sea.