Background: Personal security alarms have been used to try to reduce violence against healthcare staff, some of whose members face relatively high risks of assault. This systematic review focused on the effect of alarms in reducing the incidence and/or severity of assaults. Methods: Electronic databases, including Cochrane Library, Ovid MEDLINE(R); CINAHL Plus (EBSCO); PubMed; PsycINFO (OvidSP) PsycEXTRA; Applied Social Sciences Index and Abstracts (ProQuest) (1987 to current); Criminal Justice Abstracts (EBSCOhost); Psychology and Behavioural Science Collection (EBSCOhost); Social Policy and Practice (OvidSP) Sociological Abstracts; ProQuest theses and dissertations, were searched. Study designs eligible for inclusion were randomised controlled trials, interrupted time series and controlled before-after studies that assessed the impact of personal security alarms on assaults. Searches were undertaken for studies of healthcare staff in all settings (i.e. including staff working in confined spaces such as hospitals and also field personnel such as community health workers). Workplace violence between colleagues (lateral violence and bullying) and other uses of personal alarms (e.g. fall alarms for the elderly, domestic violence prevention) were excluded. Search results were screened by title, abstracts and keywords for possible inclusion. Full text reports for all potentially relevant studies were obtained and independently assessed for final inclusion. The primary outcome was physical assaults (recorded or self-reported). Secondary outcomes included increased confidence or self-efficacy in violence prevention (recorded or self-reported). Main results: No studies were found that met all inclusion criteria. Four reported associations of personal alarms (and other variables) with risks of assault in healthcare settings. These were described narratively. Conclusions: Healthcare workers in emergency departments, psychiatric units and geriatric facilities face much higher risks of assault than those in other healthcare settings. Alarm systems vary widely. Alarm systems form one of a range of measures, which may interact with one another, that are used to reduce the risks of assault. Given this complexity and diversity, prior to field trials EMMIE orientated efficacy trials are recommended to try to establish whether alarms can be introduced and operated in ways that can contribute to reducing assaults in specific high-risk settings. In relation to findings relating to any given intervention, EMMIE refers to effects produced, mechanisms activated to produce the effects, moderators or contexts relevant to the activation of mechanisms, implementation issues that arise, and economic costs and benefits.