We investigated whether child temperament (negative emotionality, 5 months) moderated the association between maternal stimulation (5 months--2½ years) and academic readiness and achievement (vocabulary, mathematics, and reading). We applied structural equation modeling to the data from the Quebec Longitudinal Study of Child Development (N = 1121-1448; mostly Whites; 47% girls). Compared to children with low negative emotionality, those with high negative emotionality had higher levels of academic readiness (6 years) and mathematics achievement (7 years) when exposed to high levels of maternal stimulation ([Beta] = 3.17, p < 0.01 and [Beta] = 2.91, p < 0.01, respectively). The results support the differential susceptibility model whereby highly emotionally negative children were more susceptible to the influences of low and high levels of maternal stimulation in academic readiness and mathematics achievement's developments.