Abstract: This study sought to find out the influence of family size and family birth order on academic attainment of adolescents in higher institution. The sample comprised of 102 pre-degree students of University of Ado-Ekiti, Nigeria. The population of pre-degree students was 1000, including males and females. Survey method was used to elicit information from the subjects. Experts in tests and measurement guidance and counselling validated the self constructed questionnaire while, test re-test method was employed in establishing reliability for the instrument. The reliability coefficient was 0.69; this was considered high enough for the study. The data collected was subjected to statistical tests, specifically Analysis of Variance (ANOVA). The analysis of the data showed that family size and birth order have no influence on academic performance of pre-degree students of the University of Ado-Ekiti, Nigeria.