Background. Teachers are the builders of the society and their Quality of Life may significantly impact on the psychological well-being and educational attainment of the child. The evidence from the literature suggests that Subjective Quality of Life is poor among school teachers and is influenced by socio-demographic characteristics and mental illness. However, no previous study has addressed the Subjective Quality of Life of secondary school teachers, and its relationship to socio-demographic characteristics and psychiatric morbidity in Nigeria. Aims and Objectives. The aim of this study was to measure subjective Quality of Life and its relationship to psychiatric morbidity and socio-demographic factors in public secondary school teachers in Abeokuta, Ogun state. Methods. It was a two-stage cross-sectional study carried out among selected public secondary school teachers in Abeokuta, Ogun state. Three hundred and sixty (360) teachers in 10 randomly selected public secondary schools were included in the study. The first stage involved the administration of a socio-demographic questionnaire, the World Health Organization Quality of Life (WHOQoL-BREF) and the 12-item General Health Questionnaire (GHQ-12), to all consenting teachers to measure their subjective Quality of Life and to screen for probable ii psychiatric disorder. In the second stage, subjects who were GHQ-positive and a proportion of those who were GHQ-negative were assessed using the Mini international Neuropsychiatric Interview-plus to diagnose major depressive disorder, generalized anxiety disorder, somatization disorder, pain disorder and hypochondriasis. Results The mean scores of the various domains of Quality of Life of the secondary school teachers were; physical (70.7+12.9), environment (61.7+13.4), social (72.0+12.9) and psychological (72.2+11.2). Sixty-three (18.5%) subjects were GHQ-positive (had a probable psychiatric morbidity). Using the Horvitz-Thompson estimator, the estimated true prevalence of psychiatric morbidity for a two-stage study was calculated as 21.9%. The prevalence of major depressive disorder, generalized anxiety disorder, somatization disorder, pain disorder and hypochondriasis were 11.1%, 5.9%, 5.6%, 12.9% and 0.9% respectively. The univariate analysis showed that age (F = 4.15, df = 337, p = 0.007), length of years of service (F = 3.69, df = 336, p = 0.006) and salary grade level (F = 3.62, df = 338, p = 0.03) had significant association with the environment domain of QoL. Marital status (F = 3.79, df = 338, p = 0.02) showed significant association with the social domain of QoL. While the teacher’s school category (F =3.31, df = 338, p = 0.03) was significantly associated with the psychological domain of QoL. The multivariate linear regression analysis, found that subjects who had spent the longest number of years in the teaching service had the best QoL on the environment domain (ß = 5.041, t = 2.538, p = 0.012), the married teachers had the best QoL on the social domain (ß = 6.210, t = 2.698, p < 0.007) while teachers in junior secondary schools had the best QoL in the psychological domain (ß = 4.205, t = 2.143, p =0.033). The study also found significant associations between probable psychiatric morbidity, definitive psychiatric morbidities and the domains of subjective Quality of Life. iii Conclusion. The study showed that the subjective Quality of Life among the sample of school teachers was strongly influenced by their length of years of service, marital status and teacher’s school categories. It also showed that there was a high prevalence of probable and definitive psychiatric morbidity among secondary school teachers and this correlated negatively to Subjective QoL. There is a need to focus on policies and practices that will help in the improvement of QoL of school teachers, and in the development of preventive strategies against mental illness and in providing treatment for persons with psychiatric disorders in the work place.