IntroductionAdolescent girls and young women (AGYW) in sub-Saharan Africa are at high risk of HIV acquisition. Pre-exposure prophylaxis (PrEP) demonstration projects observe that AGYW uptake and adherence to PrEP during risk periods is suboptimal. Judgemental interactions with healthcare workers (HCW) and inadequate counselling can be barriers to PrEP use among AGYW. Improving HCW competency and communication to support PrEP delivery to AGYW requires new strategies.Methods and analysisPrEP Implementation for Young Women and Adolescents Program-standardised patient (PrIYA-SP) is a cluster randomised trial of a standardised patient actor (SP) training intervention designed to improve HCW adherence to PrEP guidelines and communication skills. We purposively selected 24 clinics offering PrEP services under fully programmatic conditions in Kisumu County, Kenya. At baseline, unannounced SP ‘mystery shoppers’ present to clinics portraying AGYW in common PrEP scenarios for a cross-sectional assessment of PrEP delivery. Twelve facilities will be randomised to receive a 2-day training intervention, consisting of lectures, role-playing with SPs and group debriefing. Unannounced SPs will repeat the assessment in all 24 sites following the intervention. The primary outcome is quality of PrEP counselling, including adherence to national guidelines and communication skills, scored on a checklist by SPs blinded to intervention assignment. An intention-to-treat (ITT) analysis will evaluate whether the intervention resulted in higher scores within intervention compared with control facilities, adjusted for baseline SP scores and accounting for clustering by facility. We hypothesise that the intervention will improve quality of PrEP counselling compared with standard of care. Results from this study will inform guidelines for PrEP delivery to AGYW in low-resource settings and offer a potentially scalable strategy to improve service delivery for this high-risk group.Ethics and disseminationThe protocol was approved by institutional review boards at Kenyatta National Hospital and University of Washington. An external advisory committee monitors social harms. Results will be disseminated through peer-reviewed journals and presentations.Trial registration numberNCT03875950