The study investigated the Effect of blended learning (BL) on Students Academic Achievement in Biology in Ebonyi State. Three (3) research questions guided the study, and three (3) null hypotheses were formulated and tested at the 0.05 level of significance. The design used was a quasi-experimental, pre-test and post-test non-equivalent control group design, for a population of 496 SS1 biology students in Ikwo L G. A. of Ebonyi State. The sample size was 83 students from intact classes of two schools. One school was randomly assigned to the experimental group and taught using BL, while the other was assigned to the control group and taught with the lecture method. The instruments used to collect data for the study were the Biology Achievement Test (BAT), face-validated by experts in biology education, and measurement and evaluation. The reliability index of BAT, determined using the Kuder-Richardson formula (KR-20), was 0.80. Research questions were answered using mean and standard deviation, while Analysis of Covariance (ANCOVA) was used for testing the formulated hypotheses. The findings of the study were that BL was more effective than the lecture method in enhancing the academic achievement of the students in biology; there was no significant difference in the academic achievement scores of male and female students when taught biology with BL; there was no interaction effect of methods and gender on the academic achievement of the students in biology. The study recommended Government funding of educational training and the provision of adequate computers at schools for staff and students’ blended learning in schools.