Atmospheric CO2 enrichment can affect plants directly via impacts on their performance, and indirectly, by environment-specific traits passed down from the mother plant to the offspring. Such maternal effects can significantly alter plant species composition, especially in annual ecosystems where the entire community is recruited from seeds each year. This study assessed impacts of future, high CO2 (440 and 600 ppm) and pre-industrial, low CO2 (280 ppm) on seed traits and offspring performance in three plant functional groups (grasses, legumes, forbs) comprising 17 annual species of a semi-arid Mediterranean community. In grasses, seed size and seed-reserve utilization as expressed by root elongation tended to be higher at high than at low maternal CO2, but total seed protein concentration and protein pool decreased with increasing maternal CO2. The response of seed size to high CO2 increased with increasing leaf-mass fraction in grasses, and decreased with decreasing concentration of leaf non-structural carbohydrates in legumes. Offspring development was studied at ambient CO2, and showed reduced emergence success of high-CO2 progeny compared with low-CO2 progeny in forbs. Total biomass was lower in high-CO2 than in low-CO2 offspring across all functional groups. The biomass response to high maternal CO2 in legume offspring correlated inversely with seed size, resulting in up to 25% lower biomass in large-seeded species. Under the scenario of maternal effects combined with projected changes in biomass and seed production under direct exposure to high CO2, legumes might gain and forbs and grasses might lose from future CO2 enrichment. Most changes in seed traits and offspring performance were greater between pre-industrial and near-future CO2 than between near- and remote-future CO2 concentrations. Hence, maternal effects of increasing CO2 may contribute to current changes in plant productivity and species composition, and they need to be considered when predicting impacts of global change on plant communities.