Background: Talking about past experiences with parents is generally thought to promote positive psychological adjustment in children. Less is known about parent-child co-reminiscing when discussing past traumatic experiences, such as natural disasters, a unique type of shared trauma that can have long-lasting, and variable, psychological impacts on children and families. Objective: The current study examined the association between qualities of parent-child co-reminiscing and children's posttraumatic stress symptoms (PTSS) following exposure to a devastating tornado. Method: Forty-nine children ages 8-12 years (49% female; 78% White/Non-Hispanic) and their mothers who experienced a category EF-5 tornado in May 2011 participated in this study and provided joint recollections about their tornado experiences approximately 14-18 months post-tornado. Children also provided individual recollections about their tornado-related experiences. Individual recollections were coded for negative and positive emotion words and parent-child conversations were coded for maternal acknowledgement of child generated content. Results: Maternal acknowledgement moderated the link between children's use of both positive and negative emotion words and child tornado-related PTSS, such that children's use of both positive and negative emotion words was associated with higher levels of PTSS but only at lower levels of maternal acknowledgment. Conclusions: Maternal acknowledgement of child expressions may be a protective factor for disaster-exposed children. Understanding how children and parents discuss trauma experiences, and how aspects of discussions are associated with youth mental health, may ultimately inform interventions to help children and parents communicate following disaster exposure in a way that promotes optimal growth and recovery.