BACKGROUND: Atypical hemolytic uremic syndrome (HUS) is a rare form of thrombotic microangiopathy (TMA) characterized by complement dysregulation. Cocaine use has been reported to be a potential trigger of TMA; however, the underlying mechanisms remain poorly elucidated. Proposed hypotheses include direct endothelial injury, activation of the complement cascade, and the unmasking of whether HUS is genetic or acquired. CASE REPORT: We report the case of a 47-year-old man who presented with hypertensive emergency and acute kidney injury following intranasal cocaine use. The laboratory findings were consistent with microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and markedly elevated lactate dehydrogenase (LDH) levels. Renal biopsy (RB) revealed classic features of TMA, including glomerular capillary thrombosis, fibrinoid necrosis, and acute tubular injury. Complement studies demonstrated reduced levels of Factor I, indicative of complement dysregulation. The patient was treated with therapeutic plasma exchange and four weekly doses of eculizumab, resulting in hematologic remission and significant improvement in renal function, without the need for dialysis. Genetic testing for known atypical HUS-associated mutations was negative; therefore, maintenance therapy with eculizumab was discontinued without clinical relapses. DISCUSSION: This case underscores cocaine as a rare but important precipitating factor for atypical HUS in predisposed individuals. Early diagnosis, RB, and complement evaluation were essential in determining the etiology and guiding targeted therapy. Complement inhibition with eculizumab was effective in halting disease progression and preventing long-term renal damage. CONCLUSIONS: This case highlights the relevance of considering cocaine use as a potential trigger of complement-mediated TMA. Early identification of aHUS features and prompt initiation of complement inhibition therapy may be critical to preventing irreversible kidney injury.