Immune checkpoint inhibitors (ICIs) are a key treatment for advanced non-small cell lung cancer (NSCLC), but most patients will ultimately experience disease progression due to acquired resistance to ICI. Clinically, it is relevant to differentiate between systemic progression (SP) and oligoprogression (OP). Following SP, ICI treatment is usually discontinued, while in OP, patients are preferably treated with local ablative treatment with continuation of the ICI treatment. However, with progressive disease, it remains difficult to differentiate between true OP or SP. Circulating tumor DNA (ctDNA) analysis provides an accurate real-time reflection of the tumor burden. It remains elusive if ctDNA abundance and/or dynamics can discriminate between OP and SP. Therefore, the aim of this exploratory cohort study is to evaluate whether the sequential molecular tumor profiling of ctDNA is suitable for discriminating between true OP and SP in advanced NSCLC. Patients with stage III/IV NSCLC showing progression after ≥3 months of ICI were included. OP was defined retrospectively by RECIST response ≥ 6 months after local treatment and continued ICIs. Serial plasma samples were analyzed using the AVENIO ctDNA Expanded NGS assay targeting 77 cancer-related genes. Twenty patients (6 OP, 14 SP) were included. Somatic alterations were detected in 16 patients (median 4 mutations). No significant differences in baseline ctDNA levels, changes at progression, or mutation patterns were observed between OP and SP. Although ctDNA levels generally decreased early after the start of ICI treatment, and were increased at disease progression, mutational profiles of the 77 genes using the AVENIO Expanded ctDNA panel did not distinguish OP from SP.