Patients with diabetes mellitus (DM) sometimes exhibited impaired immune function and aggravated infectious diseases. Urinary tract infection (UTI) is one of the major complications of DM. A systematic literature search was performed in PubMed and Cochrane Library using the following keywords: diabetes mellitus, urinary tract infection, asymptomatic bacteriuria, emphysematous pyelonephritis, emphysematous cystitis, renal papillary necrosis, and sodium-glucose co-transporter 2 (SGLT2) inhibitors. The treatment of UTI in DM patients is not different from that in non-DM patients, and asymptomatic bacteriuria should not be screened or treated. Emphysematous pyelonephritis is a life-threatening renal infection with gas in the renal parenchyma or perirenal space, and 95% of affected patients had DM. Abdominal computed tomography is useful for diagnosis and determining treatment strategies. Medical management and percutaneous drainage are standard initial treatment, and subsequent nephrectomy for non-responders is considered. Nephrectomy, as an initial treatment, should be limited to a selected group of patients with severe conditions. In contrast, antibiotics, glycemic control, and bladder drainage are adequate treatment for most cases of emphysematous cystitis. SGLT2 inhibitors significantly increased the incidence of genital tract infection, but not that of UTI, pyelonephritis, or urosepsis. Here, we present cumulative evidence about etiology and management for complicated UTI with DM, but there was little information about racial differences and further evidence focusing on Asian population will be needed.