Children with Primary (or Specific) Language Impairment (PLI) demonstrate subtle deficits in nonlinguistic cognitive processing skills such as processing speed, working memory, and sustained selective attention (SSA). Previous research has suggested that intensive language treatment may influence nonlinguistic cognitive skills, particularly attention. The present study explored this hypothesis to inform future treatment studies and to provide a unique perspective on cognitive-linguistic interaction in children with PLI. A single-subject multiple-baseline design was used to track changes in key nonlinguistic cognitive processing skills before and during language treatment for three school-aged children with PLI. Results were mixed across tasks and participants, with stronger evidence for change on the working memory and processing speed tasks than on SSA. Performance variability was substantial. Results suggest that cognitive-linguistic interactions during language treatment for children with PLI may occur; however, additional research is needed, particularly studies that are sensitive to within-child performance variability.