This study examines the effect of language background on the performance of healthy participants on a battery of cognitive measures. The study was conducted as part of a larger normative study: the Macquarie University Neuropsychological Normative Study (MUNNS). A comparison was made between the test performance of three language background groups: participants from a non-English-speaking background whose first language was other than English (NESB-OE, N = 42); participants from a non-English-speaking background whose first language was English (NESB-E, N = 34); and participants from an English-speaking background (ESB, N = 40). A number of tests used in clinical neuropsychological assessment were found to be sensitive to the background of the participant, and trends in the data suggest that two factors are operating independently. It is proposed that one factor is language or proficiency in English that impacts on verbal subtests and the other is a sociocultural factor that impacts on performance or nonverbal subtests. These findings question current practices when assessing people from non-English-speaking backgrounds.