Upfront tumour genotyping is now considered an essential step in guiding treatment decision-making in the management of patients with advanced-stage non-small-cell lung cancer (NSCLC) in light of the ever-expanding toolbox of targeted therapies and immune-checkpoint inhibitors. However, genotyping of tumour biopsy samples is not feasible for all patients and, therefore, genomic analysis of circulating tumour DNA (ctDNA) has emerged as a compelling non-invasive option. Current guidelines universally recommend genotyping and support the use of ctDNA testing in certain settings, although they often omit the detail necessary for integrating these tests into clinical care on an individual basis. In this Perspective, we describe the rationale, promise and challenges associated with ctDNA-based NSCLC genotyping and suggest a framework for the implementation of these assays into routine clinical practice. We also offer considerations for the interpretation of ctDNA genotyping results, which, particularly when using next-generation sequencing panels, can be nuanced. Through the addition of this new approach to clinical practice, we propose that oncologists might finally be able to utilize effective genotyping in nearly all patients with advanced-stage NSCLC.