The primary aim of the current study was to test the effect of the presentation design of a test alert system on healthcare workers’ (HCWs’) decision-making regarding blood-borne virus (BBV) testing. The secondary aim was to determine HCWs’ acceptance of the system. An online survey used a within-subjects research design with four design factors as independent variables. The dependent variable was clinical decision. Ten realistic descriptions of hypothetical patients were presented to participants who were asked to decide whether to request BBV testing. The effect of a pre-set course of action to request BBV testing was significant when additional information (cost-effectiveness, date of last BBV test or risk assessment) was not presented, with a 16% increase from 30 to 46% accept decisions. When risk assessment information was presented without a pre-set course of action, the effects of cost-effectiveness (27% increase) and last test date (23% decrease) were significant. The main reason for declining to test was insufficient risk. HCWs’ acceptance of the test alert system was high and resistance was low. We make recommendations from the results for the design of a subsequent real-world trial of the test alert system.