Parents of children with autism spectrum disorder (ASD) are at risk for poor couple relationship quality. The goal of the current study was to understand actor and partner associations between daily level of parenting stress and perceived couple interactions using a 14-day daily diary in 186 families of children with ASD. A comparison group of 182 families of children without a neurodevelopmental disability was included to determine if actor and partner associations differed in a context of child ASD. On each day of the 14-day diary, parents independently rated their daily level of parenting stress (7-point scale) and reported on the perceived presence of different types of positive (e.g., hugged and kissed) and negative (e.g., critical comment) couple interactions. Multilevel models were used to examine actor and partner effects, and their interaction, in mothers and fathers and by group (ASD vs. comparison). Results indicated that actor daily level of parenting stress negatively covaried with perceived positive couple interactions in mothers in both groups. In contrast, actor daily level of parenting stress positively covaried with perceived positive couple interactions in fathers in the ASD group. There was a significant interaction between actor and partner daily level of parenting stress for perceived negative couple interactions in both mothers and fathers. Specifically, one's own daily level of parenting stress was more strongly positively related to her/his perceived negative couple interactions on days when her/his partner also had high parenting stress. This interaction was stronger in mothers in the ASD versus comparison group. Implications for family interventions are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).