The study investigated the relationship between teaching space planning and students' academic performance in Lagos State senior secondary schools. The study adopted a descriptive and correlation design type. Stratified random sampling technique was used to select 300 respondents comprising principals, teachers and students from schools in Education District II of Lagos State, Nigeria. In each school, 1 principal, 4 teachers and 20 students were selected from the 12 sample schools selected for the study. Three hypotheses were formulated and to guide the study. A self-constructed questionnaire titled Teaching Space Planning Questionnaire (TSPQ) and record observation of Students' West Africa Senior School Certificate Examination (WASSCE) results of May/June from 2009-2011 were used to collect relevant data. The questionnaire was validated by experts in the field of research. The reliability coefficient of 0.78 was obtained using split-half reliability method to test the reliability of the questionnaire. Pearson's product-moment correlation statistics was used with the aid of SPSS (version 20) to test all the null hypotheses at 0.05 significance level. Analysis of data revealed that a significant relationship exists between teaching space planning, classroom planning, laboratory planning and students' academic performance in Lagos State senior secondary schools. It was recommended that government and all stakeholders should give necessary financial and professional support to the secondary schools toward ensuring good teaching space planning as this will facilitate good academic performance of the students. Furthermore, educational planners and administrators should intensify efforts at ensuring that adequate provision is made in the budget for more provision of teaching space specifically class rooms among others.