There is no gold standard for making the diagnosis of autoimmune hepatitis (AIH), and the diagnosis of acute onset AIH (A-AIH) is most challenging. A-AIH sometimes develops into acute liver failure with poor prognosis if the diagnosis is delayed. Therefore, it is most important for the better prognosis to diagnose non-severe A-AIH early and treat appropriately. However, features in the early stage of A-AIH are unclear. We examined initial characteristics of non-severe A-AIH in detail and tried to find novel clinical features for the early diagnosis. Clinical, biochemical, immunological, radiological, and histological features of 71 patients (54 women, mean age 57.9±14.3years) with non-severe A-AIH admitted to community hospitals between 2001 and 2022 were analyzed retrospectively. Forty-six had no symptom on onset and liver injuries were discovered by regular medical checkups. The mean duration from onset to consultation was 25.0±29.3days. Liver histology showed acute hepatitis in 59% and chronic hepatitis in 41%. Patients with symptoms revealed more male sex (P=0.039), higher alanine aminotransferase (P<0.001), higher total bilirubin (P<0.001), and higher rate of histological acute hepatitis (P=0.0013) than those without symptoms significantly. Male sex, presence of symptoms on onset, occurrence of jaundice in the course, and histological acute hepatitis were correlated. Sixty-five percent of non-severe A-AIH patients were asymptomatic on onset, suggesting that A-AIH would develop insidiously and present a longer clinical course than that reported. Male patients more often revealed true acute hepatitis clinically, biochemically, and histologically than female ones.