Diagnostic testing of speech/language skills in the African languages spoken in South Africa is a challenging task, as standardised language tests in the official languages of South Africa barely exist. Commercially available language tests are in English, and have been standardised in other parts of the world. Such tests are often translated into African languages, a practice that speech language therapists deem linguistically and culturally inappropriate. In response to the need for developing clinical language assessment instruments that could be used in South Africa, this article reports on data collected with a Northern Sotho non-word repetition task (NRT). Non-word repetition measures various aspects of phonological processing, including phonological working memory (PWM), and is used widely by speech language therapists, linguists, and educational psychologists in the Western world. The design of a novel Northern Sotho NRT is described, and it is argued that the task could be used successfully in the South African context to discriminate between children with weak and strong Northern Sotho phonological processing ability, regardless of the language of learning and teaching. The NRT was piloted with 120 third graders, and showed moderate to strong correlations with other measures of PWM, such as digit span and English non-word repetition. Furthermore, the task was positively associated with both word and fluent reading in Northern Sotho, and it reliably predicted reading outcomes in the tested population. Suggestions are made for improving the current version of the Northern Sotho NRT, whereafter it should be suitable to test learners from various age groups.