The study examined the instruction between two independent variables of Teacher Quality and Instructional Strategy on Students Performance in Secondary School Science. In trying to examine the problem of this study, three null hypotheses were generated for testing at 0.05 level of significance Factorial Analysis of variance design with one dependent variable and two independent variables at two levels. The t-test was used in the analysis of the result. One hundred and twenty Senior Secondary School Three (S.S.S. III) Students and Twelve Biology Teachers randomly selected from six Schools in Ethiope East and Ukwuani Local Government Areas of Delta State were used as subjects for this. The result showed that the variables of teacher quality and instructional Strategy had positive significant relationship with achievement in science. Moreover, it was found that Teacher quality and Instructional strategy were two non-separate interactive independent variables in science Education. Thus, efforts should be made by all concerned with teachers' recruitment, training, certification, and science Education in general to ensure that these two variables are properly integrated into the teaching and learning of Science subjects in Secondary Schools. (Contains 3 tables.)