This study explores the processes by which custodial mothers can support and inhibit fathers' relationships following divorce and separation. It draws on qualitative interviews with resident mothers and nonresident fathers from 54 separated families, including 22 sets of former couples. The study found that mothers adopt a range of strategies, from proactive gate opening to gate closing, and that these strategies appear influential. Maternal perceptions of paternal competence and child welfare beliefs, parental relationship quality, and parental role bargains were strongly linked to different types of maternal gatekeeping. Informed by systems theory, the interviews of former couples suggest that gate work, whether gate opening or gate closing, can be a dynamic transactional process rather than a linear and unidirectional process running from mothers to fathers.