There is a well-documented interdependency between destructive interparental conflict (IPC) and parenting difficulties (i.e., spillover effect), yet little is known about the mechanisms that "carry" spillover between IPC and parenting. Guided by a cascade model framework, the current study used a longitudinal, multimethod, multi-informant design to examine a process model of spillover that tested whether parental executive functioning (working memory, cognitive flexibility, inhibitory control) served as a mediator of the prospective associations between IPC and subsequent changes in parenting over a 2-year period. Mothers and fathers were separated into differentiated models and multiple domains of parenting were examined (i.e., authoritarian discipline and scaffolding behavior). Participants included 231 families (both mothers and fathers of preschoolers). Race was reported as White (62%), Black (21%), Mixed (8%), Asian (3%), or Other (6%) and 14% considered their ethnicity to be Hispanic/Latino. Median household income was $65,000. Results indicated that for fathers, IPC indirectly predicted domain-general parenting difficulties (increased authoritarian parenting and decreased scaffolding) via deficits in paternal cognitive flexibility (but not inhibitory control or working memory). In mothers, IPC directly predicted domain-specific parenting difficulties (decreased scaffolding only) that did not operate via maternal executive functions. Notably, these effects occurred over and above the influence of parental socioeconomic status. This study constitutes a first step toward documenting parental executive functioning as a mechanism underlying the spillover of IPC to the parent-child relationship. Family interventions intended to interrupt IPC spillover should emphasize father involvement and consider targeting parental executive functions as change mechanisms.