This quantitative study investigated self-reported sleep, mental health and trauma related nocturnal behaviours among South Sudanese Australians (SSA), examined sex differences in their responses, and sought to determine risk factors for insomnia in this population. Comparisons were also made to a general Australian (AUS) sample of 1,512 respondents, obtained in a previously published study using the same questions regarding sleep difficulties. Self-reports of sleep difficulties, psychological distress (Kessler Psychological Distress Scale, K10), and nocturnal post-traumatic stress symptoms (Pittsburgh Sleep Questionnaire Inventory-Addendum, PSQI-A) were obtained from 117 former refugees (aged 16-60 years) who had been resettled for a decade on average. A key finding was that SSA men (n = 62) reported many more problems compared to both SSA women and AUS men. These problems included high rates of clinical insomnia (32%), clinical-level nocturnal post-trauma symptoms (57%), restless legs (31%), daytime sleepiness (40%), fatigue (43%), and waking unrefreshed (55%). Nearly one in five SSA men had "very high psychological distress," a rate 10 times higher than that of men in Victoria and twice as high as SSA women. Analyses suggest that for many SSA men memories and dreams of past traumas may be affecting sleep health, with some improvement over time. It was concluded that men within the South Sudanese Australian community report hitherto unrecognised significant problems with their sleep. The findings are consistent with the interpretation that unresolved pre-migration trauma stress may be affecting the sleep of about half of the South Sudanese men in Australia.