The term ‘toxic trio’ was coined to describe the risk of child abuse and neglect stemming from a combination of domestic violence, parental mental health issues and/or learning disability, and parental alcohol and/or drug misuse (Brandon, 2009). Although concerns about the language have been raised in some quarters, it has become a dominant reference point in children's social care in England and, to an extent, internationally over the past two decades. It has become embedded in the family justice system, child protection assessment processes and national data collection. There is evidence that each factor in isolation can lead to worse child outcomes, although this is of mixed quality and far from comprehensive. This article reports the results of a systematic review of evidence relevant to the relationship between the ‘toxic trio’ factors in combination and child maltreatment, identifying 20 papers. Despite the term's currency, we found little quality evidence of the incidence of the ‘trio’ factors in child maltreatment, little consideration of intersectionality and almost no theoretical examination of the supposed relationships. Such studies as have been conducted have too rarely taken into account, or controlled for, contextual factors, such as the socioeconomic circumstances or the ethnicity of the families, or children's ages. The discrepancy between the priority given to the ‘toxic trio’ and the paucity of the evidence-base makes a case for a shift away from over-simplified attributions of parental risk in policy and practice, and towards greater attention being given to other significant factors for child protection.