Data available indicated that the performance of students in Chemistry has continued to be poor over years, especially in national exams (KCSE). Despite the interventions and measures offered by the ministry of education to employ qualified teachers to teach Chemistry in secondary schools, poor performance persists in some schools within Dagoretti South Constituency. This study was “School Environmental Factors Influencing the Performance of Students in Chemistry in Public Secondary Schools in Dagoretti South Constituency, Nairobi”.This study was guided by the following research objectives: the influence of teaching and learning resources on students' academic performance in Chemistry, the effects of teaching methodology on students' academic performance in Chemistry, and the extent to which student’s attitudes affect their academic performance in Chemistry, and the extent teachers’ qualification influence learning of Chemistry in Dagoretti South Constituency, Nairobi. This researchadopted a descriptive survey design and purposive sample techniques to select the schools and simple random sampling to select class teachers and students that participated in the study. The study was conducted in three Public Secondary Schools in Dagoretti South Constituency; one Boys’ Secondary School, one Girls’ Secondary School, and one Mixed Secondary School. The research sample included 126 participants drawn from the target population; 116 student participants from the three schools; form 3 and form 4 students, 7 Chemistry teachers, and principals of the sampled schools. Simple random and purposive sampling methods were used for data collection and the data collected was organized and analyzed using the latest version 28 of the Statistical Packages for the Social Science (SPSS). Data were presented using frequency tables, pie charts, and graphs. The study discovered that schools have equipped laboratories but teachers do not conduct practicals regularly for students.Negativeattitudes of students toward Chemistry influence theirperformance.The teachers use mostly the question-and-answer method in teaching. The study recommended that the school administration should ensure that the methods used by the teachers are effective and evaluated at the end. Teachers should incorporate other methods in the teaching and learning process and also have positive attitudes toward the students. Students should make efforts to study more the subject and have positive attitudes toward it.