Purpose Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in cancer patients. However, the association of VTE with immunotherapy remains poorly defined. We therefore evaluated the frequency of VTE in patients receiving immunotherapy and tried to determine predisposing factors. Methods A total of 133 adult metastatic cancer patients treated with immunotherapy for any cancer between were included. Baseline demographics, ECOG performance status, type of tumors, and baseline blood count parameters were recorded. Possible predisposing factors were evaluated with univariate and multivariate analyses. Results The median age was 60 (interquartile range (IQR) 48-66) years, and the median follow-up was 10.1 (IQR 5.8-18.5) months. Renal cell carcinoma (26.3%) and melanoma (24.1%) were most common diagnoses. Fifteen patients (11.3%) had an episode of VTE. Most of the VTEs were diagnosed as pulmonary emboli (10/15; 67%). Eighty percent (12/15) of these VTE cases were detected incidentally. Patients with a baseline ECOG performance status of 1 or more (29.3% of patients) had a significantly increased risk of venous thrombosis (ECOG >= 1 vs. 0, HR: 3.023, 95% CI: 1.011-9.039, p=0.048). Other factors, including patient age, tumor type, body mass index, baseline thrombocyte, neutrophil, and lactate dehydrogenase levels were not significantly associated with VTE risk. Conclusions In this study, we observed VTE development in more than 10% of immunotherapy-treated patients and increased VTE risk in patients with poorer ECOG status. With the asymptomatic nature of VTEs in most cases, a high index of suspicion level for VTE is required in patients treated with immunotherapy.