The current study examined whether socioeconomic status (SES) and chaos in the home mediate the shared environmental variance associated with cognitive functioning simultaneously estimating genetic influences in a twin design. Verbal and nonverbal cognitive development were assessed at 3 and 4 years for identical and same-sex fraternal twin pairs participating in the Twins Early Development Study (TEDS). Verbal and nonverbal skills were measured using the McArthur Scales of Language Development (VERBAL) and the Parent Report of Children's Abilities (PARCA), respectively. SES and chaos were assessed via questionnaire. Results suggest that SES and CHAOS mediate an independent and significant, but modest, portion of the shared environment for VERBAL and PARCA at Ages 3 and 4.