The increasing complexity of advanced-stage cancer management, coupled with the growing availability of targeted therapies, necessitates innovative approaches to treatment decision-making. The Belgian Approach for Local Laboratory Extensive Tumor Testing (BALLETT) study evaluated the feasibility and impact of implementing comprehensive genomic profiling (CGP) across multiple laboratories and integrating genomic data into clinical decision-making for patients with advanced cancers. This prospective, multi-center study enrolled 872 patients with advanced solid tumors across 12 Belgian hospitals. CGP was performed using a standardized next-generation sequencing panel across nine laboratories, with results reviewed by a national molecular tumor board (nMTB) for treatment recommendations. CGP was successfully performed in 93% of sequenced patients (756/814), with a median turnaround time from inclusion to nMTB report of 29 days. Actionable genomic markers were identified in 81% of patients, substantially higher than the estimated 23% if restricting to nationally reimbursed panels. The nMTB provided treatment recommendations for 69% of patients with successful CGP. Of those with recommendation uptake data available (n = 454), 23% received the matched treatment. Reasons for non-implementation included physician’s choice (27%), trial not conducted at an acceptable distance (21%), and rapid clinical deterioration (12%). CGP also revealed potential germline variants in 15% of cases, prompting recommendations for genetic counseling. The BALLETT study demonstrates the feasibility of implementing standardized CGP across multiple laboratories and its potential to identify actionable targets in a majority of patients with advanced cancers. However, the translation of genomic findings into clinical practice faces challenges, including drug access and the need for improved decision-support tools. These findings underscore the importance of addressing implementation barriers to fully realize the potential of precision oncology in routine clinical care.