IgA Nephropathy (IgAN) is one of the most common forms of glomerulonephritis, yet treatment options remain limited for patients who cannot tolerate immunosuppressive therapy. The management becomes particularly challenging in the context of active infection, such as syphilis, where immunosuppression poses significant risks. Finerenone, a novel non-steroidal Mineralocorticoid Receptor Antagonist (MRA), presents a promising non-immunosuppressive strategy to reduce proteinuria and slow the progression of Chronic Kidney Disease (CKD). We report the case of a 35-year-old woman with biopsy-proven IgAN (Oxford classification M0E0S0T0-C0) and persistent proteinuria, despite treatment with sacubitril-valsartan, dapagliflozin, hydroxychloroquine, and prednisone. Further immunosuppression was limited by complications including urinary tract infection and blurred vision. The patient was subsequently diagnosed with neurosyphilis based on neurological manifestations and cerebrospinal fluid findings. Given the contraindication to enhanced immunosuppression, finerenone was initiated as an add-on therapy. After titration to a daily dose of 20 mg, her proteinuria significantly decreased to below 100 mg/24h, without inducing hyperkalemia or reducing glomerular filtration rate. The treatment was well-tolerated, and no drug interactions were observed with concurrent penicillin therapy for syphilis. This case illustrates that finerenone may serve as an effective and safe adjunctive treatment for reducing proteinuria in IgAN, especially in complex clinical scenarios where standard immunosuppressive therapies are contraindicated or poorly tolerated-such as in the presence of an active concurrent infection.