Coaching parents to use language facilitation strategies improves long-term language outcomes for autistic children. To optimize parent-mediated interventions, more studies need to explore factors that influence parents' learning. This study involved 119 autistic children (18-48 months) and their biological mothers enrolled in a single-site, factorial randomized clinical trial. Mothers were taught to use one of two types of language facilitation strategies (responsive or directive) during eight weekly, hour-long instructional sessions. We explored the impact of (a) type of language facilitation strategy, (b) maternal Broad Autism Phenotype (subclinical traits of autism spectrum disorder), and (c) preintervention strategy use on mothers' outcomes measured immediately and 3 months after intervention sessions. At postintervention, mothers who learned responsive strategies demonstrated significantly greater use of taught strategies than mothers who learned directive strategies (d = 0.90, 95% CI =[0.47, 1.32]). Mothers' use of taught strategies did not differ by Broad Autism Phenotype status. However, a significant two-way interaction was found between preintervention strategy use and Broad Autism Phenotype status on taught strategy use (F(1, 107) = 6.04, p = 0.016, [delta]R[superscript 2] = 0.053). Findings suggest that strategy type, maternal Broad Autism Phenotype status, and preintervention strategy use may be important factors to be considered to individualize parent-mediated interventions.