Sentence repetition and non-word repetition tests are widely used measures of language processing which are sensitive to language ability. Surprisingly little previous work has investigated whether children's socio-economic status (SES) affects their sentence and non-word repetition accuracy. This study investigates sentence and non-word repetition using an adaptation of the Grammar and Phonology Screening (GAPS) test. The sample comprised 126 typically-developing Spanish-monolingual Chilean children aged 5;6 from low (n = 65) and high (n = 61) socio-economic status (SES) families. The results revealed that the high SES group scored significantly higher than the low SES group in the sentence repetition task, but there was no group difference for non-word repetition. The high SES group also scored significantly higher on a measure of vocabulary comprehension, and when vocabulary comprehension was taken into account, the group difference in sentence repetition was no longer significant. The authors examine how the differential effect of SES on sentence and non-word repetition might be explained by differences in the language and cognitive mechanisms involved in the two tasks, and discuss the clinical implications of their findings.