Numerous health hazards characterize the profession of a seafarer. The job-specific environment may affect the crews’ well-being and mental health. The options for health promotion are limited, as seafarers are isolated for long periods and are a difficult-to-reach collective. A digital app-based health management system might offer a promising approach in this regard. This study aims to identify seafarers’ technical competencies as a prerequisite for possible health app-based health promotion. A total of 976 seafarers (response rate 75.1%) on 65 ships of a Hamburg shipping company completed the standardized questionnaire MDPQ-16 (Mobile Device Proficiency Questionnaire) that assesses the IT competence in 8 different sub-scales. The results were stratified in respect to occupational groups aboard as well as compared to a reference collective ashore. The seafarers had an MDPQ-16 sum-score of 4.40 (SD 0.84), scoring 0.21 points higher than the land-based reference collective. Significant differences were observed between the ratings and officers in almost every sub-scale and item of the MDPQ-16. The highest sum-score was held by the nautical officers with 4.71. Greater differences between officers and ratings were observed in sub-scales related to rather complex tasks. The seafarers demonstrated a high level of IT proficiency, even surpassing the land-based sample, suggesting that their technical competence is adequate for app-based health promotion. In view of the higher scores of officers, the selection of health apps has to be tailored to the seafarers’ different levels of mobile competence in order to maximize the improvement in mental health and well-being. Further research is needed to determine seafarers’ needs and interests.