Understanding different cardiometabolic safety profiles of antipsychotics helps avoid unintended outcomes among young patients. We conducted a population-based study to compare cardiometabolic risk among different antipsychotics in children, adolescents and young adults. From Taiwan’s National Health Insurance Database, 2001–2013, we identified two patient cohorts aged 5–18 (children and adolescents) and 19–30 (young adults), diagnosed with psychiatric disorders and newly receiving antipsychotics, including haloperidol and sulpiride, and second generation antipsychotics (SGA, including olanzapine, quetiapine, risperidone, amisulpride, aripiprazole, paliperidone, and ziprasidone). Risperidone users were considered the reference group. We analyzed electronic medical records from seven hospitals in Taiwan and confirmed findings with validation analyses of identical design. Primary outcomes were composite cardiometabolic events, including type 2 diabetes mellitus, hypertension, dyslipidemia, and major adverse cardiovascular events. Multivariable Cox proportional hazards regression models compared cardiometabolic risk among antipsychotics. Among 29,030 patients aged 5–18 and 50,359 patients aged 19–30 years, we found 1200 cardiometabolic event cases during the total follow-up time of 37,420 person-years with an incidence of 32.1 per 1000 person-years. Compared to risperidone, olanzapine was associated with a significantly higher risk of cardiometabolic events in young adults (adjusted hazard ratio, 1.57; 95% CIs 1.13–2.18) but not in children and adolescents (1.85; 0.79–4.32). Specifically, we found young adult patients receiving haloperidol (1.52; 1.06–2.20) or olanzapine (1.75; 1.18–2.61) had higher risk of hypertension compared with risperidone users. Results from validation analyses concurred with main analyses. Antipsychotics’ various risk profiles for cardiometabolic events merit consideration when selecting appropriate regimes. Due to cardiometabolic risk, we suggest clinicians may consider to select alternative antipsychotics to olanzapine in children, adolescents and young adults.