Family systems theory points to the interconnected nature of dyadic relationships within the family unit, arguing for attention to how the parental relationship shapes their ties to and interactions with their children. Grounded in family systems theory, we consider how relationship churning—defined as being in an on-again/offagain relationship with the same partner—is associated with father involvement. We use data from the Fragile Families and Child Wellbeing Study to examine how father involvement among relationship churners compares with father involvement among those in three other relationship types (measured during the first five years of the focal child’s life): stably together relationships, stably broken-up relationships, and repartnered relationships. First, we find that churning fathers remain more involved with their 9-year-old children than do parents who stably break up or repartner, but they are less involved than those who are stably together. Second, lower relationship quality among churners—and, to a lesser extent, repartnering and childbearing with a new partner—explains some of the differences in father involvement between churners andthe stably together. Third, these differences are most apparent among parents not living together when father involvement is measured. Taken together, the focus on relationship churning extends prior research on the association between relationship transitions and father involvement by separating relationship instability from partner change.