Introduction: Acute glomerulonephritis (AGN) in children is typically characterized by hematuria, oedema and hypertension. In Sri Lanka, most common cause for AGN in children is post streptococcal, typically characterized by elevated antistreptolysin-O titre (ASOT) and low complements (C3) level. However, atypical presentations with normal complement levels andalternative infectious triggers may pose diagnostic challenges. Case presentation: We report an 11-year-old previously healthy girl who presented with a threeday history of fever and painless macroscopic hematuria. She had no edema, oliguria, or hypertension on admission. Three weeks prior, she experienced an upper respiratory tract infection with sore throat and erythematous rash. No features of connective tissue disorders.Investigations revealed significant hematuria, proteinuria, elevated inflammatory markers (ESR, CRP), elevated ASOT (1200 IU), and transient renal impairment. She was initially managed as post-streptococcal glomerulonephritis (PSGN). However, serum complement levels (C3 and C4) remained normal from onset, which was atypical. Mycoplasma antibody titre was markedly elevated (1:640). During hospitalization, she developed transient hypertension which resolved with supportive care. Ultrasound imaging showed bilaterally edematous kidneys consistent with acute parenchymal changes. She was treated with supportive nephritic management,blood pressure control, intravenous ceftriaxone, and oral clarithromycin. Renal function and inflammatory markers gradually normalized over six weeks without complications. Conclusion: Atypical nephritic presentation with normal complement levels should prompt evaluation for alternative infectious triggers. Broader etiological consideration, including Mycoplasma infection, is essential to avoid diagnostic anchoring in atypical cases of acute glomerulonephritis. Follow up of patients with AGN is important to detect chronicity and complications.