This paper systematically reviews literature to date about how child welfare workers' decisions about neglect are influenced by their environments. We conducted a systematic search of Web of Science, Embase, PsycInfo, Scopus, and Applied Social Sciences Index & Abstracts, looking for studies in English of any methodology, published since the 1989 Children Act, in which statutory thresholds in England are defined. We used child welfare workers' definitions of neglect or, in the absence of this, defined "neglect" as harmful acts of omission by a caregiver (failure to do something necessary for a child's well-being). We included the views of child welfare practitioners with or working toward a social work qualification and those completing statutory child protection investigations, whatever their qualifications. Thirty-nine studies met the criteria for review. Quality was assessed using the Mixed Methods Appraisal Tool and Gough's Weight of Evidence framework. Themes were identified iteratively and synthesized using a narrative method. The review found evidence that high caseloads and work-related stress might result in neglect receiving lower priority for intervention. The threshold for statutory intervention also appears to be influenced by the availability of non-statutory support services. These findings suggest that greater investment in services, particularly early intervention, may help children experiencing neglect receive sufficient, timely, and proportionate support. We also found that practitioners find it challenging to evidence neglect, and this can result in delays intervening, suggesting that practitioners may benefit from training and support in court skills.