Background: Advanced practice providers (APPs) play important roles in enrolling, educating, and caring for patients in clinical trials. However, much remains unknown about the role of APPs in managing adverse events (AEs) in early (phase I to II) clinical trials. In this study, we assessed the outpatient management of grade 3 to 4 AEs by APPs in early trials and characterized the workflow of our APP Phase I to II Fast Track (FT) Clinic. Patients and Methods: We retrospectively reviewed records of patients with advanced or metastatic solid tumors enrolled in phase I to II clinical trials who were seen by APPs from September 2017 to August 2018 in the APP phase I to II FT clinic in the Department of Investigational Cancer Therapeutics. Results: A total of 808 patients enrolled in 159 clinical trials were seen in 2,697 visits (median 3 visits per patient; range 1–28) by 10 APPs. Treatment was interrupted in 6.9% of visits, and grade 3 to 4 AEs were seen in 5.4% of visits; however, patients from 1.4% of visits were sent to the emergency center (EC) and/or admitted. Patients referred to the EC and/or admitted were more likely to have baseline hypoalbuminemia, high lactate dehydrogenase, and poor Eastern Cooperative Oncology Group performance status (i.e., ECOG > 1; p < .001). There were no associations between EC referral and gender, APP years of experience, or type of treatment. Conclusions: The APP Phase I to II FT Clinic has an important role in the management of AEs by APPs in early clinical trials in the outpatient setting, potentially avoiding EC visits and admissions.