Background: Human cytomegalovirus (CMV) is associated with aspergillosis, but the simultaneous presence of CMV viral interleukin-10 (cmvIL-10) and aspergillosis has never been investigated. CmvIL-10 is produced by CMV-infected cells and acts as an immune modulator during CMV infection. The aim of this study was to evaluate cmvIL-10 levels in peripheral blood and its influence on the clinical outcomes of Aspergillus infection. Methods: Patients who visited or were admitted to the hospital with suspected Aspergillus infection, including invasive aspergillosis (IA) and chronic pulmonary aspergillosis (CPA), were prospectively enrolled. The cmvIL-10, human IL-10 (hIL-10), IL-1B, IL-6, IL-8, IFN-γ, and TNF-α levels in peripheral blood were measured. Results: Patients with Aspergillus infection had a higher level of cmvIL-10 than the control group (158 ± 305 vs 27.9 ± 30.4 pg/ml, p <.05). The level of cmvIL-10 was not correlated with CMV viremia or end-organ disease. The cmvIL-10 but not hIL-10 level was positively correlated with the IFN-γ level (p <.05) and marginally negatively correlated with IL-1B and IL-8 levels (p <.1). In patients with CPA, a high level of cmvIL-10 (≥100 pg/ml) was a poor prognostic factor for long-term survival (p <.05). In contrast, CMV viremia or end-organ disease was associated with poor survival in patients with IA (p =.05). Conclusions: Aspergillus infection was associated with CMV coinfection with cmvIL-10 in blood. A cmvIL-10 concentration ≥100 pg/ml was a predictor for unfavourable outcome in CPA patients.