Background: Patients with advanced epidermal growth factor receptor ( EGFR)-mutant lung adenocarcinoma (LAD) inevitably experience drug resistance following treatment with EGFR-tyrosine kinase inhibitors (TKIs). Objectives: We aimed to analyze the effect of primary tumor consolidative therapy (PTCT) on patients treated with first-line osimertinib. Design and methods: This retrospective cohort study was conducted in patients with advanced stage III or stage IV LAD with EGFR-sensitizing mutations (exon 19 deletion or L858R mutation) with disease control after first-line osimertinib. A curative dose of primary tumor radiotherapy or primary tumor resection was classified as PTCT. We compared the progression-free survival (PFS) and overall survival (OS) of patients with and without PTCT. Results: This study included 106 patients with a median age of 61.0 years, and of those, 42% were male and 73.6% were never-smokers. Exon 19 deletion was observed in 67.9%, 30.2% had a programmed cell death ligand 1 (PD-L1) tumor proportion score <1%, 33.0% had brain metastasis, and 40.6% had oligometastasis. In all, 53 (50%) patients underwent PTCT. Patients who underwent PTCT demonstrated significantly better PFS [30.3 (95% confidence interval (CI), 24.1–36.4) versus 18.2 (95% CI, 16.1–20.2) months; p = 0.005] and OS [not reached versus 36.7 (95% CI, 32.5–40.9) months; p = 0.005] than patients who did not. A multivariate analysis showed that PTCT was an independent factor associated with better PFS [hazard ratio (HR), 0.22; 95% CI, 0.10–0.49; p < 0.001] and OS [HR, 0.10; 95% CI, 0.01–0.82; p = 0.032]. The PFS benefits of PTCT were consistent across subgroups, and the HR tended to be lower in patients aged <65 years, males, smokers, stage IVB disease, L858R, PD-L1 expression ⩾1%, non-oligometastasis, and brain metastasis. Conclusion: Of the patients with advanced EGFR-mutant LAD, those who underwent PTCT had a significantly better survival outcome than those who did not. The survival benefits were consistent across different subgroups.