We present a case of invasive fungal co-infection in a young patient treated for an acute myeloid leukemia and having undergone a twice-haploid matched unrelated donor hematopoietic stem cell transplantation (HSCT) with two different donors. A mucormycosis diagnosis was made shortly after the patient's admission using imagery and specific Mucorales qPCR which was treated with liposomal amphotericin B and posaconazole. Twenty days later, a blood culture was positive for Fusarium solani, and disseminated cutaneous lesions appeared. The antifungal treatment was changed to liposomal amphotericin B and voriconazole. Thanks to a complete hematological reconstitution and despite a co-infection with two aggressive filamentous opportunistic fungi, the patient recovered. We took advantage of this clinical case to test a specific Fusarium solani qPCR, which proved to be promising when performed retrospectively on some of the patient samples.