<p>Increasing automation in the maritime industry is transforming job demands from predominantly physical to cognitively intensive tasks, underscoring the need to better understand factors influencing mental workload. This pre-registered systematic review follows PRISMA guidelines and synthesises 51 empirical studies on mental workload in maritime contexts. It proposes a framework of four overarching categories – system-related, task-related, external, and individual or organisational – comprising 21 factors. These factors demonstrate that maritime tasks such as navigation, communication, and port manoeuvres are particularly associated with high mental workload, depending on additional factors such as experience, role responsibilities, and environmental conditions. The effects of automation on mental workload are currently examined only in relation to the level of automation, system design, and system reliability. This review highlights the ongoing complexity of traditional maritime work alongside the emerging requirements of digitalisation and automation, underscoring the necessity of re-examining traditional influencing factors within this evolving context. The study emphasises the importance of integrating user-centred system design and targeted training to optimise mental workload in future maritime workplaces. Significant methodological heterogeneity across the reviewed studies underscores the need for robust, interdisciplinary approaches to advance beyond descriptive findings.</p>