Forty native Spanish-speaking children (age 8;0-10;3), 20 with Specific Language Impairment (SLI) and 20 with Typical Language Development (TLD), received a battery of psycholinguistic tests, IQ, hearing screenings, and the Spanish Non-word Repetition Task (NRT). The children's repetition of 20 non-words was scored. The percentage of correct non-words was significantly lower in children with SLI than in age-matched children with TLD. A length effect was found, with the subset of three-, four-, and five-syllable non-words leading to greater differences between groups. The NRT identified SLI accurately; likelihood ratios are reported with significant good sensitivity and specificity. Significant positive correlations were found, for all children together, between the overall NRT accuracy and the eight contemporary expressive/receptive language scores: PPVT-III, TTFC-2, and CEG tests; WISC-IV/Vocabulary subtest; and four ITPA subtests, including lexical fluency and comprehension of sentences/stories. The Spanish NRT can be used as a diagnostic marker for SLI. The clinical implications of phonological working memory links to psycholinguistic abilities are discussed.