This study investigated the effect of computer assisted instruction on upper basic ii students’ achievement in Social studies in Nasarawa Local Government Area of Nasarawa State, Nigeria. The study employed a quasi-experimental research design in which a pre-test and post-test was used to compare the outcomes of students exposed to computer assisted instruction with those that received instructions through conventional teaching method. Two research questions and hypotheses guided the study. The population of the study comprised 5700 JSS II students and a sample of 110 JSS II students and two intact classes were used in the study. The instrument used for data collection was titled: Social Studies Achievement Test (SOSAT).The achievement test is a 40 items multiple-choice questions. The instrument was validated by three lecturers. A reliability coefficient of 0.75 was obtained. The data were analyzed using mean and standard deviation and analysis of covariance (ANCOVA). The findings of the study include a significant difference in the mean achievement scores of students taught Social Studies using computer assisted instruction and those taught with conventional teaching method. Therefore the study recommended that computer assisted instruction should be adopted by teachers in teaching Social Studies to enhance students’ achievement in the subject.