This study assessed the relation between mother mental state language and child desire language and emotion understanding in 15–24-month-olds. At both time points, mothers described pictures to their infants and mother talk was coded for mental and nonmental state language. Children were administered 2 emotion understanding tasks and their mental and nonmental state vocabulary levels were obtained via parental report. The results demonstrated that mother use of desire language with 15-month-old children uniquely predicted a child's later mental state language and emotion task performance, even after accounting for potentially confounding variables. In addition, mothers' tendency to refer to the child's over others' desires was the more consistent correlate of mental state language and emotion understanding.