A 49-year-old woman with no inflammatory bowel disease history presented to our clinic with abnormal liver function tests and right upper quadrant abdominal pain. Blood tests revealed a mixed pattern of liver injury. Abdominal magnetic resonance imaging demonstrated hepatomegaly with periportal edema and hyper-enhancing bile ducts without any sign of biliary obstruction or stricturing. Screening for viral hepatitis and autoimmune liver diseases was negative. An elevated immunoglobulin G (IgG) level suggested the possibility of autoimmune hepatitis (AIH), and a biopsy confirmed the presence of severe interface hepatitis with necrotic areas and focal lymphoid nodular formation. IgG4 staining revealed marked IgG4-positive plasma cell infiltration. A diagnosis of IgG4-associated seronegative AIH was made, and the patient was started on prednisone and azathioprine, with rapid resolution of the enzyme abnormalities. This clinical vignette highlights the potential challenges in establishing a diagnosis of IgG4-associated AIH and cholangitis, as demonstrated by the importance of confirmatory histopathology. Clinicians should maintain a high index of suspicion when confronted with a mixed pattern of liver injury with elevated immunoglobulins but seronegative autoimmune markers.