This study investigated the relationship of English language proficiency and IQ scores of low achieving Mexican American students at ages between 7 and 12 whose native language was not English. The research was designed to determine if IQ differences would be found between males and females and if a correlation exists between language proficiency and IQ scores and academic scores, respectively. It was also designed to determine which variables were statistically significant in a model utilizing gender, age, English language proficiency level, and IQ scores to predict academic achievement. Predictive models differed in significant variables found by gender. Criterion sampling was utilized to determine participation (N = 137). The students had previously been administered the Kaufman Assessment Battery for Children, Second Edition (KABC-II) for IQ assessment, the California English Language Development Test for language competency assessment, and the Woodcock-Johnson Tests of Achievement, Third Edition (WJ-III ACH) for academic achievement assessment. The results indicated a significant difference of IQ scores between males and females within this age range (7-12). Correlational analysis indicated that English language proficiency did have a significant relationship with IQ scores. ANOVA found significant differences of IQ among the five levels of the CELDT and age did not seem to have an impact on this relationship. Furthermore, there was a significant relationship between IQ and academic achievement, with the strongest relationship in Mathematics and Writing skills. Finally, the regression equations that emerged from the analyses differed by gender with variable subcategories of the CELDT. The results provided the understanding of the relationships among IQ, English language proficiency, and academic achievement in this special population. The study also recommends English language assessment strategies for low achieving Mexican American elementary students.