The study investigated the influence of English proficiency on Junior Secondary School Achievement in Social Studies in Osun State, Nigeria. The research was a correlational type. The population for this study consisted of all the Junior Secondary Schools in Osun State, Nigeria. A total number of 100 students were randomly selected from two public Junior secondary Schools in Ife East Local Government that comprises 50 students in each of the schools. Data were collected with two set of questionnaires administered on the 100 students that were sampled for the study. The first set of questionnaire was on “English Language Proficiency Test” (ELPT) and the second set of the questionnaire was on “Social Studies Achievement Test” (SSAT). Two hypotheses were generated for the study and were tested using Pearson product moment correlation coefficient statistical method at 0.05 level of significant. The results showed that language proficiency were significantly related to the achievement in Social Studies. Thus, it was recommended that English language skills should be handled with high priorities by teachers and also that government should encourage the teaching of English language skills in our schools by providing adequate support or resources.