This study was carried out to investigate the extent to which teacher subject matter competence and passion for teaching correlated with students’ achievement in English vocabulary among public senior secondary students in Lagelu Local Government of Oyo State. Four research questions were answered in the study. The instruments for data collection were Achievement test in English vocabulary (r= 0.78), Teacher subject mastery scale (r= .81) and Questionnaire on teachers’ passion for teaching (0.87). Data collected were analysed using the descriptive statistics of frequency counts, simple percentages, mean and standard deviation. Also, Multiple Regression Analysis was used to determine the relationship, composite contribution and the relative contribution of the independent variable on dependent variable at .05 level. Findings revealed that there was a positive significant relationship between teachers’ subject matter competence and achievement in English vocabulary(r = 0.17); teachers’ passion for teaching and achievement in English vocabulary (r = 0.28). The joint effects of the independent variables were also found to be (R = .389 and a 2 multiple R of .184) significant at .05 level. The findings of the study further showed that the relative contribution of teachers’ subject matter competence (â = .06) and teachers’ passion for teaching (â = .28) were significant to students’ academic achievement in English vocabulary. Based on the findings of the study, it is recommended that teachers should attend regular workshops, seminars and training programmes in order to increase their content knowledge in teaching.