This paper documents the methods used to assess the implementation costs of the APPRAISE alcohol brief intervention (ABI) delivered to male remand prisoners across two study sites in Scotland and North East England. We first developed a comprehensive taxonomy of the activities constituting the APPRIASE ABI. Next, data were collected for each activity about the study staff and the subject time spent, in addition to the other resources used and unit costs. From the pilot data collection it was possible to construct a narrative, for both study sites, for how the intervention was delivered and the time required for each activity. The ABI was delivered by Change Grow Live and Humankind intervention staff and staff salaries were obtained from both organizations to calculate the staff delivery costs for each site. Other costs, such as the printing of materials, were estimated based on APPRAISE study records. Due to the ongoing Covid-19 restrictions and limited access to prison resources and staff, there were significant deviations from the initial study protocols. As a result, we document the costs of implementing the ABI as delivered rather than as planned. This paper provides the first estimates of the implementation costs of an ABI delivered in criminal justice setting in the UK. Although these costs are from a pilot implementation that was heavily impacted by the Covid-19 pandemic, this paper nonetheless provides useful, policy-relevant information on the potential costs of providing ABI to remand prisoners. It also serves as a methodological template, guidance, and proof of concept for future micro-costing studies of ABIs in criminal justice settings.