This study aimed at investigating the effects of teachers' personal and professional demographic characteristics on students' academic performance in English. To achieve this aim, the researcher used a sample of 37 English secondary teachers and 400 students in the District of Plaridel, Schools Division Office of Bulacan during the academic year 2018-2019. The researcher used the descriptive-correlational method of research, which used a researcher-made questionnaire as the primary data gathering technique. The results of the regression analysis show that the eight (8) variables of the personal demographic characteristics and the four (4) variables of the professional demographic characteristics affect students' academic performance in English to a various extent as shown by the non-zero coefficients. Results of the analysis of variance of the regression of personal and professional demographic characteristics on students' academic performance revealed an F value of 0.955 with a p-value of 0.490 and an F-value of 1.197 with a p-value of 0.331. Since the associated probability of the F-value is higher than alpha (0.05), the null hypothesis has to be sustained. This means that all variables of the personal and professional demographic characteristics do not exert significant effects on students' academic performance in English. Conclusions were drawn and recommendations were offered.