This study examined associations of school readiness measures obtained before school entry with academic achievement at early school age in children born very preterm (VPT, gestational age ≤ 30 weeks) and children born full term (FT, GA ≥ 37 weeks). The sample included 38 children born VPT and 30 born FT recruited at age 4 years and followed to early school age. Measures of readiness included tests of global cognition, executive function, motor abilities, and preacademic skills, as well as caregiver behavior ratings. Tests of math, reading, and spelling were administered to assess school-age achievement. Analyses that controlled for socioeconomic status and accounted for inclusion of siblings compared the groups on the achievement tests and identified measures of readiness related to school-age achievement. Achievement difficulties were more pronounced in the VPT group and associated with problems in multiple readiness domains. Effect sizes for these associations were largest for measures of spatial ability, executive function, and preacademic skills. Some associations remained significant when controlling for global cognitive ability at age 4 years, and others were significant only for the VPT group. Findings suggest that deficits on tests in multiple readiness domains assessed before school entry in children born VPT or FT are associated with early school-age achievement. The most pronounced readiness deficits in the VPT group at age 4 years were also among those most closely associated with later difficulties in achievement. Further research is needed to refine assessment of school readiness in children born VPT.