Fragile families are defined as those that include unmarried or romantically unstable parents who have children and are socioeconomically disadvantaged. Mothers in fragile families may experience risk factors that lead to increased depressive symptoms that inhibit their ability to bounce back after stressful events. Risk factors for poorer maternal mental health may include declines in father involvement and a lack of coparenting support. This study examined the connected nature of coparenting and father involvement over time among continuously unmarried mothers from the Fragile Families and Child Wellbeing Study. A bidirectional latent growth curve analysis demonstrated that early father involvement was associated with a more gradual decline in coparenting support over the child's first 5 years, while early coparenting support also predicted a slower decline in father involvement over time. Steeper declines in coparenting support and father involvement over time were linked with more maternal depression and lower maternal life satisfaction when their child was nine. Results demonstrate a clear need for targeted intervention with both parents in fragile families to promote involved fathering behavior and enhance coparental relationships.