Objectives HIV pre‐exposure prophylaxis (PrEP) delivery in the UK is inequitable; over 95% of PrEP users were men who have sex with men (MSM) despite making up less than 50% of new HIV diagnoses. We conducted a systematic review to identify modifiable barriers and facilitators to PrEP delivery in the UK among underserved populations. Methods We searched bibliographic/conference databases using the terms HIV, PrEP, barriers, facilitators, underserved populations, and UK. Modifiable factors were mapped along the PrEP Care Continuum (PCC) to identify targets for interventions. Results In total, 44 studies were eligible: 29 quantitative, 12 qualitative and three mixed‐methods studies. Over half (n = 24 [54.5%]) exclusively recruited MSM, whereas 11 were in mixed populations (all included MSM as a sub‐population) and the other nine were in other underserved populations (gender and ethnicity minorities, women, and people who inject drugs). Of the 15 modifiable factors identified, two‐thirds were at the PrEP contemplation and PrEParation steps of the PCC. The most reported barriers were lack of PrEP awareness (n = 16), knowledge (n = 19), willingness (n = 16), and access to a PrEP provider (n = 16), whereas the more reported facilitators were prior HIV testing (n = 8), agency and self‐care (n = 8). All but three identified factors were at the patient rather than provider or structural level. Conclusions This review highlights that the bulk of the scientific literature focuses on MSM and on patient‐level factors. Future research needs to ensure underserved populations are included and prioritized (e.g. ethnicity and gender minorities, people who inject drugs) and provider and structural factors are investigated.