It has recently been shown that children with early shigellosis are at increased risk of attention deficit/hyperactivity disorder (ADHD). This study aimed to evaluate the association between antibiotic treatment of shigellosis with long-term ADHD rates. A retrospective cohort study was conducted that included all the Leumit Health Services (LHS) enrollees aged 5–18 years between 2000–2018 with a documented Shigella-positive gastroenteritis before the age of 3 years. Of the 5176 children who were positive for Shigella gastroenteritis before the age of 3 years, 972 (18.8%) were treated with antibiotics early (<5 days), 250 (4.8%) were treated late (≥5 days), and 3954 children (76.4%) were not prescribed antibiotics. Late antibiotic treatment was associated with significantly increased rates of ADHD (adjusted OR = 1.61; 95% CI, 1.1–2.3). Early treatment with antibiotics was not associated with increased ADHD rates (adjusted OR = 1.02; 95% CI, 0.8–1.3). In conclusion, late antibiotic treatment of early childhood shigellosis was associated with increased rates of ADHD.