The Modified Checklist for Autism in Toddlers (M-CHAT) is a screening questionnaire for Autism Spectrum Disorder (ASD). Previous findings have confirmed the M-CHAT's sensitivity and specificity across several cultures, yet few studies have considered M-CHAT scores as a distributed trait in a sample of typical infants. The current study examined how the M-CHAT predicts concurrent word learning (experiment 1) as well as socio-emotional understanding (experiment 2) in 18-month-old infants. Results demonstrated that the number of items endorsed on the M-CHAT negatively correlated with the proportion of trials on which infants looked at a toy named by the experimenter as well as performance on the word learning task. In experiment 2, high scores on the M-CHAT correlated with less instrumental helping, less imitation, and a smaller productive vocabulary size.