The problem of low commitment of science teachers in Ogun State, Nigeria has been an issue of serious concern. Perhaps factors such as demographic indices of teachers could be responsible but have not been given adequate attention in literature. This study was carried out to investigate demographic indices as predictor of science teachers' job commitment in Ogun state. Four objectives consisting of two research questions and two hypotheses guided the study. Descriptive research design was employed. Study population included 172 principals and 2,617 science teachers. Sample of 90 principals and 882 science teachers were used. Researcher-constructed questionnaires titled "Demographic Indices and Teachers' Job Commitment Questionnaire‘(DIQ)’ ‘(r = 0.79)’and (JCQ)" (r = 0.82) were used. Descriptive and inferential statistics were used to analyze data. Results showed poor (bad) good teaching experience (x̅ = 2.785) and professional competence (x̅ = 2.625) and low level of science teachers' commitment to their job (x̅ = 2.104). Results also showed significant joint contribution of demographic indices on science teachers' job commitment (F3, 86 = 3.019). Furthermore, the predictors that had individual significant influence on science teachers' job commitment are good teaching experience (β = .191; t = 3.121) and professional competence (β = .169; t = 3.132) in public secondary schools in Ogun State. It was recommended among others that educational stakeholders should try their best possible to improve demographic indices in order to increase science teachers' job commitment.