In this research a relational study was conducted to examine the link between phonological working memory (PWM) and specific aspects of linguistic proficiency in adult speakers of Spanish as a foreign language (SFL). PWM was measured with a nonword repetition test based on the Chilean variant of Spanish. Proficiency levels were determined with a test that evaluated six specific aspects of language use from the Program of Spanish as a Foreign Language from Universidad de Concepción (ELE-UdeC). A statistically significant correlation was found between aspects of proficiency and measures of PWM in the group of the longest and final-stress-patterned stimuli. A significant linear association was also observed when the aspect of similarity to real language words was added to the analysis; all aspects of proficiency, except for reading comprehension, correlated statistically with the performance of PWM in the group of the longest, final-stress-patterned and low similarity to real words stimuli. These findings provide new evidence supporting the relationship between PWM and SFL performance, in line with some of the findings recently published for other languages.