Background: Commercial fishing at sea is among the world’s most dangerous occupations. With 24- hour cycles of physically demanding work, adequate rest and recovery are often elusive in deep-sea commercial fishing. Human trafficking in the fishing industry has been identified as a problem in the Greater Mekong Subregion (GMS), with reports documenting 18-24 hour work days and severe violence. As a largely unregulated sector with activities conducted in international waters far from shore and outside of national jurisdiction, the commercial fishing industry poses unique risks to workers health, safety and well-being. Yet, research on the health needs of trafficked fishermen is sparse. Moreover, extraordinarily little research exists on policy responses to this problem. This thesis aims to investigate the health needs of trafficked fishermen, and understand how victim identification and assistance are being conducted in Thailand, a key transit and destination country for fishing trafficking. Methods: The thesis comprises four studies: i) a systematic review of the literature on occupational health among GMS migrant and trafficked fishermen and other seafarers; ii) a quantitative exploration of factors associated with work-related injuries and violence among labour-trafficked men that used post-trafficking services in the GMS; iii) a mixed methods study examining the health needs of trafficked fishermen and health service provision; and iv) a qualitative study examining how potentially trafficked fishermen are identified and assisted by frontline responders to trafficking in Thailand. Results: The systematic review found limited research on occupational hazards faced by migrant and trafficked fishermen and seafarers. Findings from quantitative analysis of a cohort of labour-trafficked males from different sectors indicated that work-related injuries were associated with severe violence and being trafficked for fishing. Ever having experienced violence was associated with being in the fishing sector and fluency in the language of the destination country. Having documents did not appear to be protective against injuries or violence. The mixed methods study found that dizzy spells and exhaustion were common among trafficked fishermen. There were strong associations between physical health symptoms and severe violence, injuries, or detention by immigration authorities. Trafficked fishermen are perceived by boat captains to be disposable when injured or sick. While health can be a means to reach trafficked men, health and welfare providers faced challenges including language barriers and negotiating payment for services for uninsured fishermen and accident compensation with employers. The qualitative study found that frontline responders perceived trafficking to take place outside of Thai waters and that migrant brokers caused employers to inadvertently traffick men. Confusion about whether debt bondage or withholding of documents counted as trafficking indicators may be linked to ambiguous inclusion of these indicators in policy documents. Institutional constraints included limited staff with increased remits and interpreter shortages. Conclusion: There is evidence that trafficked fishermen face more extreme occupational hazards and abuse compared to men trafficked into other sectors, with a high burden of physical and mental ill-health experienced. Promising strategies employed by health and welfare providers to reach men highlight the importance of targeted outreach. Beliefs about the locus of the problem and institutional constraints among frontline responders indicate that further training on trafficking indicators, as well as institutional change, is needed to improve victim identification and assistance.