The study investigated the relationship between students socio-economic background and Mathematics achievement in some senior secondary schools in Southwestern Nigeria. The study adopted the descriptive survey design that employs simple frequencies and percentages for the analysis of the data. Four research questions were answered in the study. The subjects for the study were 1722 students senior secondary two mathematics students selected from 36 schools from each of the senatorial districts in Southwestern Nigeria. Two research instruments were used for data collection. The findings revealed that majority of the students lived with their father and mother only and they have the basic things needed in a house for good education. The findings also revealed that the parents of the students lived mainly in the urban areas and are educated with private businesses of their own; have investments ranging from stocks and shares to owing houses. Also the results showed that majority of the students were of average academic ability in mathematics. With a conducive environment like this, students academic achievement in mathematics should be better than students, who do not have such facilities.