The majority of the existing research dedicated to the mother–child narrative interaction has focused on biological families during the co-construction of autobiographical narratives and has consistently shown that the mothers’ narrative support has an important influence on children’s narrative participation and overall development. The current study aimed to compare adoptive mothers’ narrative support and children’s narrative participation in different types of narrative tasks. Specifically, we analyzed the narrative interaction between 30 preschool-aged children and their adoptive mothers during the co-construction of two autobiographical narratives and one fictional narrative. We also explored the influence of the mothers’ use of elaborative and repetitive narrative dimensions, as well as the children’s sex, early adversity, and language development in children’s narrative participation. The results revealed that the adoptive mothers tended to use the elaborative dimension more in the fictional narrative than in the autobiographical ones. For the adoptive mothers’ use of the repetitive dimension and the children’s narrative participation, no significant differences were found between the three narrative tasks. Additionally, the results showed that the adoptive mothers’ use of the elaborative dimension significantly predicted children’s participation in the autobiographical narratives, while their use of the repetitive dimension significantly predicted children’s participation in the fictional narrative. The results of this study highlighted the relevance of the adoptive mothers’ ability to adapt their narrative support to the specific type of narrative task, as well as how such support may enhance or hinder children’s narrative participation during the co-construction of both autobiographical and fictional narratives.