Transfeminine patients facing barriers to gender confirming surgery sometimes pursue illicit feminization procedures such as "street" hormones and silicone injections. These procedures often yield complications and disfigurement, making surgeons and insurance companies wary of secondary breast reconstruction. This clinical series assesses illicit treatment among our transfeminine breast surgery patients and describes the presentation, surgical approaches, and outcomes of each patient. A retrospective review of transfeminine patients who underwent chest feminization surgery with a single provider between March 2018 and March 2020 identified patients with a history of illicit hormones or silicone injections. Demographics, comorbidities, preoperative diagnoses and symptoms, surgical details, and postoperative outcomes were collected. Patients were contacted for a follow-up survey concerning outcomes and satisfaction. Of the 41 transfeminine patients reviewed, eight (19.5%) had previous illicit treatment. Seven (17.1%) used non-prescribed hormones, and three (7.3%) received silicone breast injections. Two patients presented with symptoms from silicone injections; the remaining were asymptomatic. Six patients underwent subglandular breast augmentation, one had a reduction mammoplasty, and one underwent an implant exchange. Only one patient had postoperative complications that healed without surgical intervention. This series emphasizes the need to assess the prevalence of silicone injections and illicit hormone use among transgender chest feminization patients. The use of these substances was relatively high in our population compared to national averages; however, there is a low risk of postoperative complications. Providers may perform breast surgery in patients with a history of illicit augmentation practices after careful evaluation and surgical planning.