The health of inmates living in a restricted environment are affected by oral health behaviours and is related to their oral health-related quality of life (OHRQoL). We investigated oral health behaviours and oral symptoms among male inmates and analysed factors related to OHRQoL. Three hundred and seventy-six male inmates in two prisons were investigated using a self-reported questionnaire. The survey items included oral health behaviours, oral symptoms, self-esteem, and OHRQoL level. We analysed cross-correlations and factors related to OHRQoL. Toothbrushing after lunch and dinner was practiced by 83.5% of male inmates. ‘Food impaction’ was experienced by 45.4%. The OHRQoL level among male inmates was low, at 39.90 points. A hierarchical multiple regression model that controlled for general characteristics identified the following OHRQoL factors, in order of significance: trouble biting/chewing (β = -0.307), toothache (β = -0.154), temporomandibular joint disorder (β = -0.099), and periodontal health (β = 0.089). Self-esteem and OHRQoL were not significantly correlated. To ensure oral health in male inmates, the results of this study suggests that an oral health education programme, as well as provision of adequate dental care services, is required to increase appropriate oral health practice rates.