Many studies have shown that invasive pulmonary aspergillosis, cryptococcosis, and mucormycosis can mimic radiographic and clinical features of primary lung cancer. However, more research surveying the incidence and outcomes of these fungal infections among patients with a history of lung cancer is needed. The aim of this study was to describe the occurrence and clinical outcomes of opportunistic invasive fungal infections that can mimic tumors in non–small-cell lung cancer patients. Patients seen at Stanford University Medical Center from January 1, 2007, to May 1, 2020, with pulmonary aspergillosis, cryptococcosis, or mucormycosis after non–small-cell lung cancer (NSCLC) diagnosis were reviewed. The European Organization for Research and Treatment of Cancer National Institute of Allergy and Infectious Diseases Mycoses Study Group criteria was used to classify patients with evidence of proven or probable invasive fungal infection within our cohort. A total of 12 patients with proven or probable invasive mold infection (including 8 cases of aspergillosis) and 1 patient with proven cryptococcosis were identified, without any cases of mucormycosis. Of this cohort, 6 patients (46%) showed radiographic findings that were found to be most consistent with lung cancer by radiologists. Eight cases (62%) were suspected of cancer recurrence or progression by the treatment team on the basis of additional considerations of medical history and clinical symptoms. Most patients had active NSCLC or had a history of recurrence without active NSCLC at the time of fungal discovery (11 patients; 85%). Most patients died without full recovery (7 patients; 54%). Invasive pulmonary aspergillosis and cryptococcosis can often be mistaken as cancer recurrence or progression in patients with a history of NSCLC because of mimicking radiographic and clinical characteristics. Presentations of opportunistic fungal infections, including invasive pulmonary aspergillosis, cryptococcosis, and mucormycosis, can mimic radiographic and clinical manifestations of pulmonary neoplasms. In patients with a history of lung cancer, these findings may initially be presumed to reflect cancer recurrence or progression. In this retrospective study, we aimed to study the occurrence and nature of invasive pulmonary aspergillosis, cryptococcosis, and mucormycosis in patients with a history of non–small-cell lung cancer. In our cohort, 62% of proven or probable aspergillosis or cryptococcosis were initially suspected to be metastatic or recurrent cancer by treatment teams, underscoring the importance that fungal infectious diseases should be considered as part of the differential diagnosis of new pulmonary lesions.