Although non-native English speakers have been defined as a single distinct group in the most research literature, it has been relatively recently argued that they extensively vary in socio-cultural background, socio-economic status (SES), and parental education background wherein they grow cognitively. The present research, therefore, was designed to investigate the potential role of SES and parental education background in predicting Iranian English as a foreign language (EFL) learners' performance on reading and listening comprehension tasks. A non-experimental, correlational design was adopted and data were gathered from a total number of 300 Iranian senior high school EFL learners. Reading and listening comprehension was examined via a modified TOEFL reading comprehension subtest and a short listening test. The results indicated that correlations between the learners' SES and parental education background as well as between their reading and listening comprehension scores were meaningful statistically. Furthermore, based on multiple regression calculations, it was found that the highest parental education level was the strongest predictor of listening and reading comprehension. Implications for policies and practices were discussed.