Neuropsychiatric systemic lupus erythematosus (NPSLE) is a severe complication of systemic lupus erythematosus (SLE), characterized by heterogeneous neurological manifestations. Current therapies, such as plasma exchange (PE), are limited by cardiovascular risks and resource availability. This case report explores peritoneal dialysis (PD) as a novel dual-purpose therapy for NPSLE, combining renal support with immunomodulation. Case Presentation: A 42-year-old female with SLE presented with recurrent lower limb edema and dyspnea for 1 year, worsening over 2 weeks, followed by seizures. PD initiation alongside immunosuppressive therapy resolved neuropsychiatric symptoms and stabilized cardiorenal function. Proteomic Findings: PD fluid analysis showed significant down-regulation of complement-related proteins (FCER2 and CRP) on the fourth day after initiation of PD, suggesting PD attenuates neuroinflammation by targeted clearance of proinflammatory mediators. Conclusion: PD may serve as a viable adjunct therapy for NPSLE through modulation of complement overactivation.