Data concerning the incidence of invasive aspergillosis (IA) in high-risk patients in Greece are scarce, while the impact of the revised 2020 EORTC/MSGERC consensus criteria definitions on the reported incidence rate of IA remains unknown. A total of 93 adult hematology patients were screened for IA for six months in four tertiary care Greek hospitals. Serial serum specimens (n = 240) the sample was considered negative by PCR were collected twice-weekly and tested for galactomannan (GM) and Aspergillus DNA (PCR) detection. IA was defined according to both the 2008 EORTC/MSG and the 2020 EORTC/MSGERC consensus criteria. Based on the 2008 EORTC/MSG criteria, the incidence rates of probable and possible IA was 9/93 (10%) and 24/93 (26%), respectively, while no proven IA was documented. Acute myeloid leukemia was the most (67%) common underlying disease with most (82%) patients being on antifungal prophylaxis/treatment. Based on the new 2020 EORTC/MSGERC criteria, 2/9 (22%) of probable and 1/24 (4%) of possible cases should be reclassified as possible and probable, respectively. The episodes of probable IA were reduced by 33% when GM alone and 11% when GM + PCR were used as mycological criterion. The incidence rate of IA in hematology patients was 10%. Application of the 2020 EORTC/MSGERC updated criteria results in a reduction in the classification of probable IA particularly when PCR is not available.