Continuous use of heavy machinery in fields and frequent farm traffic sometimes result in soil compaction. Soil compaction reduces the oxygen (O₂) concentration in soil capillaries and hence lowers the O₂ availability for germinating seeds. We investigated how reduced O₂ levels changed germination behavior of weeds to elucidate their potential to adapt to O₂-deficient soils (compacted, compressed, and waterlogged soils and soils with hard surfaces). Two similar laboratory experiments were conducted with five O₂ treatments (20.9%, 15%, 10%, 5%, and 2.5%). The germination percentage of the invasive weed hairy fiddleneck [Amsinckia menziesii (Lehm.) A. Nelson & J.F. Macbr. var. menziesii] and the common weeds common lambsquarters (Chenopodium album L.) and Persian speedwell (Veronica persica Poir) was not significantly reduced at 15% O₂. The germination of scarlet pimpernel (Anagallis arvensis L. ssp. arvensis), silky windgrass [Apera spica-venti (L.) Beauv.], catchweed bedstraw (Galium aparine L.), and knawel (Scleranthus annuus L.) was significantly reduced at 15% O₂. The highest germination was obtained at 20.9% O₂ for blackgrass (Alopecurus myosuroides Huds.), A. spica-venti, G. aparine, annual bluegrass (Poa annua L.), wild mustard (Sinapis arvensis L.), scentless chamomile [Tripleurospermum inodorum (L.) Sch. Bip.], field violet (Viola arvensis Murray) and the less common weeds A. arvensis and S. annuus. Distribution of flora in the landscape may change on O₂-deficient soils by reducing germination of some species such as A. arvensis and S. annuus and favoring others like A. menziesii and C. album. The ability to germinate at 2.5% and 5% O₂ may contribute to explain why A. myosuroides and A. menziesii have become successful as weeds on O₂-deficient soils, as they maintained a germination percentage between 34% and 58% at 2.5% O₂.