: Invasive pulmonary aspergillosis is an opportunistic mycosis, difficult to diagnose, due to the environmental fungi of the genus Aspergillus. The diagnostic tools, even if more are available, are still limited in number and effectiveness. The current recommendations issued by the EORTC/MSG (European Organization of Research and Treatment of Cancer/Mycoses Study Group) and the ECIL (European Conference for Infection in Leukemia) suggest collecting epidemiological, radio-clinical, and biological data to support the diagnosis of aspergillosis with a strong presumption. Thus, medical imaging and serum galactomannan antigen currently constitute the basis of the screening approach, although they both have some limitations in specificity. (1→3)-β-D-glucans are pan-fungal serum markers with a very good negative predictive value. Real-time PCR lacks standardization, and fungal culture from respiratory specimens is sometimes not sensitive enough. Histology allows proving the diagnosis of aspergillosis, but biopsy is not always possible in immunodepressed patients. We present the various arguments for the diagnosis of invasive aspergillosis, with a particular emphasis on recent exploration techniques.