This study determined the accuracy of "Modified Checklist for Autism in Toddlers" ("M-CHAT") in detecting toddlers with autism spectrum disorder (ASD) and other developmental disorders (DD) in community mother and child health clinics. We analysed 19,297 eligible toddlers (15-36 months) who had "M-CHAT" performed in 2006-2011. Overall sensitivities for detecting ASD and all DD were poor but better in the 21 to <27 months and 27-36-month age cohorts (54.5-64.3%). Although positive predictive value (PPV) was poor for ASD, especially the younger cohort, positive "M-CHAT" helped in detecting all DD (PPV = 81.6%). This suggested "M-CHAT" for screening ASD was accurate for older cohorts (>21 months) and a useful screening tool for all DD.