Abstract Background Immune checkpoint inhibitors (ICIs) are a novel class of antineoplastic drugs which have dramatically changed the management of non-small cell lung cancer. ICI-associated cardiotoxicity is rare, but potentially fatal, presenting in most of cases as autoimmune acute myocarditis during the first phase of treatment. However, since an extensive cardiac monitoring is not routinely performed in most immunotherapy trials, the true incidence of ICIs related cardiac effects is largely unknown. Aim Aim of our study is to ascertain a possible subclinical cardiac involvement in patients with non-small cell lung cancer treated with ICIs. Methods We prospectively recruited 40 patients (13 males; mean age 64.3 ± 8.3 years) starting immunotherapy with PD-1/PDL-1 inhibitors for non-small lung cancer between January and August 2018. Demographic and clinical data were recorded and all patients underwent a standard 12-lead ECG and a transthoracic echocardiogram with assessment of left ventricular global longitudinal strain (LV GLS). Furthermore, blood samples for pro BNP-nt and high sensitivity Troponin T (hsTnT) measurements were collected. Serial assessments were performed before and 1 and 3 months after initiation of immunotherapy. Results A history of previous coronary artery disease was documented in eight cases (20%). At follow-up no cardiovascular events were recorded. Compared with baseline, echocardiographic parameters of ventricular function did not significantly changed at 1 and 3 months (LVEF 61 ± 6% at baseline, 61 ± 5% at 1 month, 60,2 ± 5% at 3 months, p =0.1; E/E’at baseline 9.2 ± 3, 9.2 ± 2.8 at 1 month, 9.1 ±3,5 at 3 months, p = 0.2;TAPSE 20 ± 3.4 mm at baseline, 21.3 ± 2.8 mm at 1 month, 20 ± 3.8 mm at 3 months, p =0.1; LV GLS -20.3 ± 3.6% at baseline, -20.8 ± 2.3% at 1 month, -20.6 ± 3% at 3 months; p = 0.4). Analogously, no significant increase in circulating levels of cardiac biomarkers was found with hsTnT <0.015 ng/ml in all patients at baseline, 1 month and 3 months and median proBNP-nt 118 pg/ml (IQR 47-200) at baseline, 171 pg/ml (IQR 91-520) at 1 month, and 182 pg/ml (IQR 78-470) at 3 months, p = 0.9. Conclusions In our study no significant clinical or subclinical evidence of myocardial involvement was detected during treatment with ICIs in patients with non-small cell lung cancer, thus suggesting the potential cardiovascular safety of this promising class of antineoplastic drugs.