Background: Post-streptococcal glomerulonephritis (PSGN) is a common cause of acute nephritic syndrome in children. Rarely, it may result in life-threatening complications, including acute pulmonary edema and critical hyperkalemia. Case Presentation: We report a 10-year-old Yemeni girl (25 kg) presenting with severe respiratory distress, irritability, and generalized pitting edema. Laboratory tests confirmed PSGN with markedly reduced complement C3 (42.2 mg/dL) and nephritic urine sediment containing numerous red blood cells and casts. The patient developed critical hyperkalemia (7.0 mmol/L) and acute pulmonary edema, requiring urgent intubation and mechanical ventilation using pressure-controlled mandatory ventilation (P-CMV). Management: Aggressive fluid mobilization and electrolyte stabilization were initiated. High-dose intravenous furosemide (4 mg/kg/day), renal-dose dopamine (5 μg/kg/min), and potassium-lowering interventions were applied. Morphine sedation (0.1 mg/kg/dose) was administered every 4 hours during the first 24 hours, then every 8 hours for 12 additional hours, followed by withdrawal prior to extubation. Morphine effectively controlled irritability and optimized patient–ventilator synchronization. The patient produced 1700 mL urine in 17 hours, demonstrating a strong diuretic response. Conclusion: Early recognition of severe extra-renal complications in PSGN is critical. Intensive supportive care—including mechanical ventilation, meticulous fluid and electrolyte management, and appropriate sedation—is essential for survival in cases of acute pulmonary edema and critical hyperkalemia.