Lung cancer is the most common cause of cancer‑related death. Accurate and easy‑to‑use prognostic factors are necessary. Increased platelet count might be a potential prognostic factor. We aimed to investigate the relationship between thrombocytosis and stage of lung cancer and to assess the frequency and clinical importance of thrombocytosis in this patient group. We retrospectively analyzed hospital records of consecutive patients with non-small cell lung cancer (NSCLC) who underwent curative‑intent pulmonary resections. Of 323 patients, 285 patients with NSCLC were selected (mean [SD] age, 66.55 [8.52] years; men, 63.86%). Squamous cell carcinoma was diagnosed in 130 patients (45.61%); adenocarcinoma, in 128 (44.91%); large cell carcinoma, in 16 (5.61%); and adenosquamous carcinoma, in 11 (3.86%). The prevalence of preoperative thrombocytosis in the whole sample was 10.18% (n = 29). Anemia was more common in patients with thrombocytosis compared with those without thrombocytosis (65.52% vs 30.08%; P <0.001). Thrombocytosis was found in 22.41% of patients with stage III+IV cancer and in 3.82% of those with stage I (P <0.001). Moreover, in patients with no metastases (N0, M0 according to the 7th edition of the TNM classification), thrombocytosis was more frequent in the group with stage II than in that with stage I cancer (3.85% vs 20.00%; P = 0.002). Thrombocytosis was also more frequent in patients with N2 than with N1 disease (9.76% vs 23.81%; P = 0.09). Thrombocytosis is often observed in patients with NSCLC and is significantly associated with the higher stage of disease.