This study examined whether daily variations in levels of mothers’ work, home, and relationship stress were related to collaborative and oppositional qualities of mother–child conflict interactions across 1 week. Mothers reported on 1 specific conflict interaction with their 5- to 8-year-old child and their work, home, and relationship stress through online surveys each day for 7 consecutive days. Diary data from 142 mothers were analyzed in 6 multilevel models, each including within- and between-family levels of a stressor predicting collaborative or oppositional conflict qualities. Results suggested that families in the sample differed from each other, and also varied during the week, in collaborative and oppositional conflict qualities as well as stress in all 3 domains. Mothers reported a greater degree of oppositional conflict qualities on days characterized by higher perceptions of home chaos. Additionally, mothers who reported higher average levels of negativity in romantic relationships endorsed oppositional conflict qualities to a greater extent than mothers with lower relationship negativity. Two multilevel models including all 3 stressors in relation to collaborative and oppositional conflict revealed that for mothers managing multiple roles, average romantic relationship stress was the most important unique contributor to mother–child conflict qualities and daily relationship stress was particularly influential among mothers with sons compared to those with daughters. Results support the spillover hypothesis of stress within the family system and are discussed in terms of mothers’ coping mechanisms and emotional engagement.