Objective To investigate the clinical characteristics, treatment and outcomes of herpes simplex virus encephalitis-induced anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis in children. Methods The clinical data of 3 children with herpes simplex virus encephalitis-induced anti-NMDAR encephalitis treated in our department were collected, including 2 males and 1 female, aged 21 months, 10 years and 4 years, respectively. Results All the 3 children began with convulsion, accompanied by altered consciousness and abnormal behavior. Herpes simplex virus typeⅠ in cerebrospinal fluid was tested positive in all 3 cases. After antiviral and symptomatic treatment, the condition of 3 children was improved, but was aggravated again after 1 week to 1 month, with positive cerebrospinal fluid anti-NMDAR antibodies. After active symptomatic treatment, 2 children recovered well, and 1 gave up treatment and died. Conclusion Herpes simplex virus encephalitis can develop anti-NMDAR encephalitis. Dynamic detection of anti-NMDAR antibody is helpful to early identify the occurrence of autoimmune encephalitis after herpes simplex virus encephalitis, so as to intervene early.