Aspergillus-associated infection might comprise up to 23–29% of severe influenza patients from the community throughout stay in an intensive care unit (ICU). In Taiwan, cases of severe influenza with aspergillosis are increasingly reported. Therefore, we describe the relative risk of mortality among severe influenza patients with aspergillosis and other coinfections compared to severe influenza patients without Aspergillus coinfections. Methods: We retrospectively reviewed 124 adult patients with severe influenza in a tertiary medical center in southern Taiwan from January 2015 through March 2016. The definition of probable aspergillosis required abnormal radiological findings and positive Aspergillus galactomannan (GM) antigen and/or Aspergillus isolation. Results: Probable aspergillosis (detected throughout the whole course) and other coinfections (only community-acquired) were diagnosed in 21 (17%) and 38 (31%) of all patients respectively. Klebsiella pneumoniae (36.8%), Pseudomonas aeruginosa (31.6%) and Staphylococcus aureus (31.6%) were the most frequent isolates of other coinfections. In-ICU mortality of Aspergillus group (66.7%) was significantly higher than other coinfections (23.7%, p = 0.001) or control group without coinfections (15.4%, p < 0.001), with significant odds ratios after adjusting for important variables. The factor of GM index ≥0.6 had a 19.82 (95% CI, 4.91 to 80.07, p < 0.0001) odds of expiring in an ICU among the Aspergillus group. Conclusion: Dual Aspergillus and influenza infection is emerging in southern Taiwan. Meanwhile, community-acquired P. aeruginosa should be listed in the common copathogens with severe influenza. The 67% mortality linked to aspergillosis highlights the need for physicians to focus attention on patients with GM ≥ 0.6.