Although research has documented the negative effects of family transitions generally on child and maternal outcomes, transitions into and out of mothers’ relationships with partners who are not the father(s) of their child(ren) are less well understood. Through thematic analysis of semistructured interviews, this study investigated how 21 mothers and their 21 children (aged 9 to 18 years) responded to mothers’ relationship formation following the dissolution of previous relationships. Mothers tried to protect their children from the negative impact of family instability by either limiting contact with partners or maintaining continuity through continued child contact with former partners. When faced with relationship transitions, children endeavored to manage threats to their relationships with their mothers and their mothers’ former partners. When children felt they successfully managed these threats, they were more positive about their mothers’ subsequent partners. The tension between the strategies adopted by mothers and children has implications for family practitioners.