Background/Objectives: Malignant melanoma is a highly aggressive cancer associated with significant mortality, underscoring the need for continued research efforts. COMBI-EU (NCT03944356) is a prospective, non-interventional study that aims to assess adjuvant dabrafenib and trametinib usage in clinical practice, the impact of AE management, and the usage of app-based documentation on treatment adherence. Methods: Adults with complete surgical resection of stage III BRAF V600-mutant cutaneous melanoma were included. The primary endpoint was median time on treatment (TOT). Adverse event (AE) management was classified as either a high or low level of management. The rating of AE management based on a self-developed algorithm and rules from COMBI-APlus was used to analyze the impact of AE management on TOT. App-based documentation of medication intake and patient-reported outcomes (CANKADO PRO-React; version 6.0, 06.03.2019) was offered. Results: For 225 patients, the median TOT was 11.8 months (95% confidence interval [CI]: 11.7, 12.0). Treatment was completed by 138 patients (61.3%); 37 (16.4%) discontinued due to treatment-related AEs (TRAEs). TRAEs (≥1) were experienced by 181 patients (80.4%); the most common was pyrexia (38.2%). High-level AE management showed a trend toward improved treatment adherence (high versus low level: hazard ratio [HR]: 0.74; 95% CI: 0.49, 1.14); this improvement was significant with pyrexia management (HR: 0.52; 95% CI: 0.29, 0.93). Seventy-nine (35%) and 33 patients (15%) intended to use and eventually used the app, respectively. A similar proportion of patients remained on treatment for 12 months irrespective of app usage (use, 39.4% vs. non-use, 36.5%). Conclusions: High-level TRAE management showed a trend toward improved treatment adherence, which was statistically significant for pyrexia. Optional use of an app did not influence treatment adherence.