Objectives Important differences in Stage I non–small‐cell lung cancer (NSCLC) are related to the delay in the diagnosis to the treatment, hospitals' specialised status, comorbidities, tumour stage and histological type. Methods A 19‐year retrospective cohort study was conducted, including 681 patients with NSCLC in clinical‐stage IA–IB. The variables analysed were gender, age, schooling, type of health care provider, type of treatment, period of 5‐year treatment, the time between first attendance to diagnosis and the time between diagnosis and treatment, and hospital's specialised status. Results Patients who underwent radiotherapy alone had three times more risk of death than those who underwent surgery alone (adjusted hazard ratio [adjHR] = 3.44; 95% confidence interval [CI]: 2.45–4.82; p <0.001). The independent risk of death factors was being treated in nonhigh complexity centres in oncology hospitals and having started the treatment more than 2 months after diagnosis (adjHR = 1.80; 95% CI: 1.26–2.56; p <0.001) and (adjHR = 2.00; 95% CI: 1.33–3.00; p <0.001), respectively. In addition, the patients diagnosed between 2011 and 2015 had a 40% lower risk of death when compared to those diagnosed between 2000 and 2005 (95% CI: 0.38–0.94; p = 0.027). Conclusion The overall survival in curative intent Stage‐I lung cancer patients' treatment was associated with the 5‐year diagnosis group, the delayed time between diagnosis and treatment and the hospital qualification.