Abstract: We examined PrEP awareness, willingness to take it and early PrEP use among men who have sex with men (MSM) at increased risk of HIV acquisition in Belgium. This analysis of the Belgian EMIS online data of 2017–2018 adopts a cascade approach, with the following steps quantified as conditional probabilities: being eligible for, aware of, willing to take PrEP, and PrEP use. One out of three MSM was eligible to use PrEP according to the operationalized Belgian reimbursement criteria. PrEP awareness was lower among socioeconomically vulnerable MSM, MSM living outside large cities, MSM who were less open about their sexuality and those who did not identify as gay or homosexual. A lack of PrEP knowledge, a higher self-efficacy regarding safe sex, having a steady partner and reporting more symptoms of depression were related to unwillingness to use PrEP. Among those willing to take PrEP, less than one third were actually using PrEP. Not using PrEP was associated with living in small cities and experiencing financial problems.