Children's language and cognitive development are informed by adult spoken language and parental literacy behaviors, although their relative contributions have not been evaluated. Using digital audio-recorders, we unobtrusively observed the spoken language of 107 children, aged 24 to 48 months (M = 32, SD = 6.5), and their families over 3 days (M = 15.1 hours per day, SD = 1.9). Additionally, parents administered a cognitive test to their child and completed measures for their own literacy behaviors. The adult spoken language that children were exposed to accounted for 11% and 12% of the variance in their cognitive and language abilities. Parents' literacy behaviors accounted independently for 4% of the variance in children's cognitive ability but were not associated with their language ability. Parents' literacy behaviors correlated 0.33 with the quantity of adult spoken language. Our findings suggest that parents' literacy behaviors play a significant role in children's cognitive development.