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Background The proportion and impact of minimal pleural effusion (PE) on prognosis remain blurred in operable non-small cell lung cancer (NSCLC) patients who reported minimal PE on imaging. Methods Clinical and prognostic data of operable NSCLC patients who presented no distant metastasis, no direct pleural invasion, but minimal PE on preoperative imaging were retrospectively analyzed. The patients were divided into surgical (81 cases) and non-surgical (10 cases) cohorts. Potential or suspected malignant PE or pleural metastases were confirmed by surgery. The overall survival (OS) was analyzed by Kaplan-Meier curve and prognostic factors by multivariate Cox regression. Results The surgical cohort reported no pleural invasion on preoperative imaging and no pleural metastases by postoperative pathology, with an overall median disease-free survival of 36.7 (28.6, 44.7) months and a median OS of 59.8 (45.7, 73.2) months, with the latter significantly longer in the surgical cohort than in the non-surgical cohort (59.8 months vs 20.37 months, P < 0.001). Multivariate analysis indicated surgical treatment as an independent prognostic factor for OS. Conclusion Malignant PE is rare in operable NSCLC patients who report the presence of minimal PE but no distant metastasis or direct pleural invasion on preoperative imaging. Surgery may be the preferred treatment for these patients.