Purpose: To determine whether (a) expressive grammar intervention facilitated social and emergent literacy outcomes better than no intervention and (b) expressive grammar gains and/or initial expressive grammar level predicted social and emergent literacy outcomes. Method: This investigation was a follow-up to a recently published study exploring the impact of grammatical language intervention on expressive grammar outcomes for preschoolers with specific language impairment (SLI). Twenty-two 3- to 5-year-old preschoolers received ten 20-minute intervention sessions addressing primary deficits in grammatical morphology. Participants' social and emergent literacy skills were not targeted. Twelve children awaiting intervention, chosen from the same selection pool as intervention participants, served as controls. Blind assessments of social and emergent literacy outcomes were completed at preintervention, immediately postintervention, and 3 months postintervention. Results: Only intervention participants experienced significant gains in social and emergent literacy outcomes and maintained these gains for 3 months postintervention. Expressive grammar gains was the only single significant predictor of these outcomes. Conclusions: Expressive grammar intervention was associated with broad impacts on social and emergent literacy outcomes that were maintained beyond the intervention period. Gains in expressive grammar predicted these outcomes. Social and emergent literacy skills were positively affected for preschoolers with SLI during a grammatical language intervention program. (Contains 4 tables and 2 figures.)