The study looked at the adequacy of resource materials (mathematics laboratory) and its attendant effect on students mathematics achievement in some selected secondary schools in Southwestern Nigeria. The study adopted the descriptive survey design and simple percentages were used in analysing the data. Three validated instruments (QMT, SMAS and MAT) were used in collecting data for the study. The subject of the study was made up of 1750 senior secondary school students and 123 Mathematics teachers selected from 2 secondary schools in each of the Senatorial districts in Southwestern part of Nigeria. The results showed that most of the teachers (75%) have a good perception of the need and importance of mathematics laboratory in the school, while few teachers (25%) do not perceive the need to have a mathematics laboratory in the school. The result also showed that students exposed to the use of mathematics laboratory performed better (65%) than students that were not exposed to it and the level of infrastructural facilities available in the schools were very poor. The study therefore, recommends that Mathematics laboratories be established in every school and more teaching aids be provided for effective students learning .