Background: Spirituality refers to the dynamic dimension of human life that relates to the way that persons experience meaning, purpose, and transcendence. The complex task of parenting a child with a life-limiting condition may raise existential questions, which are easily overlooked by healthcare professionals. Aim: We explored how the spiritual dimension becomes manifest in parents of children in pediatric palliative care. Design: A mixed-methods systematic review was conducted, registered in Prospero (2021 CRD42021285318). Data sources: PubMed, CINAHL, Embase, PsycInfo, and Cochrane were searched for articles published between January 1, 2015 and January 1, 2023. We included original empirical studies that reported on spirituality of parents of seriously ill children, from parents’ perspectives. Results: Sixty-three studies were included: 22 North-American, 19 Asian, 13 European, 9 other. Studies varied in defining spirituality. We identified five different aspects of spirituality: religion, hope, parental identity, personal development, and feeling connected with others. All aspects could function as source of spirituality or cause of spiritual concern. Sources of spirituality helped parents to give meaning to their experiences and made them feel supported. However, parents also reported struggling with spiritual concerns. Several parents highlighted their need for professional support. Conclusions: Although studies vary in defining spirituality, reports on spirituality focus on how parents connect to their faith, others, and themselves as parents. Healthcare professionals can support parents by paying attention to the spiritual process parents are going through. More research is needed into how healthcare professionals can support parents of seriously ill children in this process.