The purpose of this study was to investigate the factors affecting students’ academic performance in geography in public secondary schools in Lang’ata Sub-County Nairobi. The objectives of the study were: to investigate whether teacher’s training and qualification on teaching and learning methods affects performance of geography students, to determine whether the availability of teaching and learning resources affect geography students' performance, to examine the extent to which the teachers' perception on teaching geography affects students' performance in geography and to determine whether student factors affect their academic performance in geography. In order to achieve these objectives, the researcher administered questionnaires to the students and teachers from selected schools in the study area. Both the students and teachers were sampled purposively to include all form three and four geography students and teachers. The study used ` and adopted a quantitative approach. The study enlisted 120 respondents comprising 100 students and 20 teachers. The Statistical Package Social Sciences (SPSS) was used to get descriptive statistics. The findings showed that most teachers used useful teaching methodology which were ideal for improving students’ performance in geography. The study noted that students had a positive attitude towards geography and found it interesting. The respondents also agreed that most schools under the study had a conducive environment for teaching and learning geography. However, most schools lacked updated and revised textbooks for teachers and students and a variety of teaching methods. Therefore, the researcher recommended that the schools administrators should strive to provide more adequate textbooks for teaching and learning geography