Middle childhood is a salient period of development (Mah & Ford-Jones, 2012). Internalising difficulties such as depression and anxiety often occur before the age of 15 (Lijster et al., 2017; Liu et al., 2011), and the burden of these difficulties continue into adolescence and adulthood (Caputi & Schoenborn, 2018; Garber & Horowitz, 2002). Previous research highlights the integral role that parent-child interactions play in the development of mental health concerns in children (Eisenberg et al., 1998; Goodman & Gotlib, 1999), with the discussion of emotions identified as a pathway which might support children’s capacity to cope with emotional distress and buffer against the development of mental health difficulties in children (Bray et al., under review; Russell et al., 2024b; Swetlitz et al., 2021). On the other hand, parents may pass on their own cognitive biases through conversations about emotions with their child (Bray et al., under review). This study aimed to examine co-rumination within parent-child conversations about past and future negative emotional events, and whether this might act as a potential pathway for the intergenerational transmission of internalising difficulties between parents and their children. Participants were parent-child dyads from New Zealand (n = 51) and Australia (n = 54). Children were aged between 8 and 12-years-old. Parents and children completed relevant measures for mental health difficulties and engaged in two reminiscing conversations (one positive and one negative) and two future event conversations (one positive and one negative). Parent-child conversations were coded for co-rumination utilising an adapted co-rumination coding scheme (Rose et al., 2014). A series of Pearson correlations and simple mediation models were conducted to examine associations between parent and child mental health and co-rumination, and to test a potential pathway of intergenerational transmission of internalising difficulties through co-rumination. Results indicated that parent and child rumination were correlated, suggesting a dyadic style of rumination developing during middle childhood. No empirical support was identified for an indirect effect of parent to child internalising symptoms through co-rumination. Recommendations for future research are discussed.