This study applied the dynamic assessment (DA) of narratives in a bilingual Spanish- and English-speaking early elementary population. We examined transfer and change in narrative performance within and across languages after mediated learning experience (MLE) in Spanish or English. Sixty-eight bilingual children were randomized to two groups: Spanish (n = 24) or English mediation (n = 25), while a control group (n = 19) participated in regular academic activities. The MLE Spanish and English groups participated in mediated learning focusing on storytelling ability, and children's modifiability was rated. Pre- to posttest narrative macro- and microstructure change was measured for all children. Both MLE groups demonstrated significant gains in macrostructure compared to the no-treatment control group. Children's stories were stronger in Spanish overall. Children in both MLE groups demonstrated transfer of narrative macrostructure across both languages regardless of the language of the MLE. When the language of MLE matched language of story production, children did not make greater posttest gains than when unmatched. Finally, MLE in English had a small effect on children's modifiability ratings. For English-language learners, DA may be a valid method to assess children's modifiability, language learning, and transfer of skills across languages in an academically relevant task.