For the past few years, the West African Examination Council (WAEC) Chief Examiners’ reports on students’ performance in mathematics have indicated that some topics (e.g. concepts of latitude and longitude) have posed a major problem for students at the senior secondary school level. This poor achievement of students in understanding the topic may be associated with the traditional “chalk and talk” method that teachers use in teaching the concept. Education reforms in recent years, have advocated for a student-centred method of teaching; a method that allows individualstudent towork at his own pace or in groups. Various researchers have encouraged the use of different forms of ICT, such as computer-assisted instruction (CAI), in the teaching of mathematics to improve students’ learning of topics in mathematics perceived to be difficult. With all the efforts concentrated on improving students’ performance in mathematics, no research studies have been conducted on the effectiveness of CAI on students’ achievement and attitude towards the learning of the concepts of latitude and longitude in Nigerian secondary schools. The study employed pre-test, post-test non-equivalent control group, quasi-experimental design involving two groups: experimental group (162) and control group (158) research design to investigate the effect of the CAI method of teaching on 2nd year senior secondary school students’ achievement and attitude to latitude and longitude.Instruments for the research study were Achievement test in latitude and longitude (ATLL); questionnaire on students’ attitude to latitude and longitude (QSALL); semi-structured interview and class observations protocol. The instruments were validated, and found reliable via a pilot study before they were employed for the main study. Datacollectedwere analysed using both the descriptive and inferential statistics to answer the research questions and to test the stated null hypotheses. Results showed a statistically significant difference in the post-test mean scores of the experimental and the control groups, whereas there was no statistally significant difference in the pre-test mean scores of these two groups. In addition, the results revealed non- significant difference between the mean scores of girls and boys in the post-test. Furthermore, there was no significant difference between science students’ post-test mean scores and their counterparts in the arts and commercial classes, and there was no interactive effect related to treatment, gender and students’ subject area in the post-test. Specifically, the knowledge in this study has added another dimension to everyday experiences of students in mathematics when the software was used to teach the perceived difficult topics, and they were actively involved in the learning process through the use of CAI techniques. The study concludes with recommendations for future research, because even though it is limited to Ogun State, it has potential for future research to be undertaken by expanding its scope to cover many other states in Nigeria. This study also recommends that efforts be made to integrate the philosophy of CAI to the teaching curriculum in Nigeiran secondary schools. Furthermore, applications of the recommendations would be appropriate for the improvement to the teaching methodology of mathematics and other science-related subjects in Nigerian secondary schools / Mathematics Education / Ph. D. (MSTE)