Mother-child emotion-related conversations, as a practice of parental socialization of emotion, can help children with autism spectrum disorder (ASD) develop socio-emotional skills. This study intends to explore relationships between mother-child conversations about emotions and socio-emotional skills of children with ASD by accounting for the moderating role of children personality traits and mothers' emotional openness. Mothers of children with ASD (n = 49) responded to five questionnaires describing their conversations about emotions, emotional openness as well as their child's socio-emotional skills and personality. We conducted hierarchical regression and moderation analyses. Our findings indicate that frequent mother-child conversations about emotions significantly predict higher emotional regulation and Theory of Mind (ToM) abilities in children with ASD (p < 0.05). Moreover, children's consciousness and openness to experience, along with mothers' emotional openness significantly moderate the relation between mother--child conversations about emotions and children's ToM skills (p < 0.05). Mother-child conversations about emotions, as a practice of parental socialization of emotion, could be beneficial for children with ASD. Children's personality traits and mothers' openness to emotion may act as a protective factor of ToM skills in children with ASD.