Invasive aspergillosis (IA) is a life-threatening infection affecting haematological cancer patients with chemotherapy-induced neutropenia. The diagnosis of IA often relies on the detection of galactomannan (GM) in serum or bronchoalveolar lavage fluid (BAL). Bi-weekly serum GM screening has been proposed for a pre-emptive therapeutic approach of IA in patients not receiving mold-active prophylaxis. We have analysed all IA cases among patients with haematological malignancies and prolonged chemotherapy-induced neutropenia (>14 days) in our institution over a 10-year period (2007-2017). Serum GM was measured twice weekly and mold-active prophylaxis was not routinely administered. Thirty IA cases were observed and a positive serum GM was the first indicator of IA in 10 (33%) of them, which represents a need of approximately 500 GM tests for the detection of a single IA case. In the other 20 (67%) cases, suggestive chest CT lesion was the first sign of IA and bronchoscopy was required in 15 (50%) cases with negative serum GM for establishing the diagnosis of probable/proven IA. A positive serum GM was associated with a worse prognosis (57% 12-week survival vs 100% among serum GM-negative patients, P = .006), irrespective of the timing of GM positivity compared to CT. We concluded that bi-weekly serum GM screening demonstrated limited benefit in this population.