We conducted a pilot randomized controlled trial of a social network-based intervention to promote PrEP adherence among transgender women (TW) in Lima, Peru. We enrolled 89 TW from six social networks and cluster-randomized them 1:1 to standard of care (n = 44) or the TransPrEP intervention (n = 45). Core workshops discussed strategies to support PrEP adherence and defined group adherence objectives. Maintenance workshops discussed participants’ experiences taking PrEP and collective adherence goals. At 3-month follow-up, we evaluated 40 participants and obtained 29 hair samples for tenofovir level measurements. Though no significant differences were observed, 36.4% (4/11) of participants of TransPrEP participants and 10.0% (1/10) of control participants had tenofovir levels > 0.023 ng/mg, consistent with ≥ 4 doses per week. 81.8% (9/11) of intervention and 40.0% (4/10) of control participants had any detectable tenofovir in their hair. Pilot assessment of our network-based intervention suggested a trend towards improved PrEP adherence, measured objectively, for TW in Peru.