To assess the efficacy of a psychoeducational intervention, Wide Awake Parenting (WAP), to decrease symptoms of postnatal fatigue.A randomized controlled trial.Local government areas within the Australian state of Victoria.Two hundred and two mothers were randomly allocated to either the professionally-led telephone support intervention (n = 63), self-directed written intervention (n = 67), or waitlist control (n = 72).The professionally-led group received a workbook, home visit, and three telephone support calls. The self-directed written group received the workbook only, and the control group received usual health care services. Primary outcomes were symptoms of fatigue, depression, anxiety and stress, and health care beliefs and behaviors. Mothers were followed up at 2- and 6-weeks postintervention.Mothers in the professionally-led group reported fewer symptoms of fatigue than mothers in the control condition at 6 weeks postintervention. Mothers in either intervention had more positive attitudes toward their health- and self-care behaviors at postintervention and follow-up. Mothers in the professionally-led intervention reported fewer symptoms of depression, anxiety, and stress than mothers in the other conditions at postintervention.Wide Awake Parenting is effective in promoting mothers' self-efficacy to prioritize, plan for, and engage in health and self-care behaviors to promote mental health and manage fatigue. Implications and future opportunities for WAP are discussed.