The study was aimed at investigating teacher-student relationship, as related to Biology achievement of senior secondary school students in Ikom Education Zone of Cross River State, Nigeria. A hypothesis was formulated to direct the study. Literature review was done accordingly. Ex-post facto research design was adopted for the study. The population of the study consisted of all the 2346 senior secondary school two (SS2) students of 2018/2019 academic session offering Biology in the 93 public secondary schools in the Zone.  The total number of public secondary schools in the zone was 93. The study adopted stratified and simple random sampling techniques. The sample consisted of 360 (SS2) biology students drawn from twelve public secondary schools using stratified and simple random sampling techniques. The research instruments were Teacher-Student Relationship Questionnaire (TSRQ) and Biology Achievement Test (BAT). The face and content validities were ensured in this study. Cronbach Alpha and Kuder Richardson formula 20 (KR-20) were the methods used for estimating reliability of instrument for the study. The reliability coefficients were 0.701 for teacher-student relationship, and 0.816 for BAT. Pearson Product Moment Correlation Coefficient was used to analyze the hypothesis at 358 degrees of freedom and 0.05 level of significance. The result indicated a significant relationship between teacher-student relationship, and academic achievement in Biology. Based on the findings, it was concluded that Teacher-student relationship in the class during teaching and learning processes influences students’ academic achievement in biology. It was recommended among others that school administrators should promote a fair teacher-student relationship in the school.