This study investigated (a) net Cu uptake kinetics in durum wheat (Triticum turgidum durum L.) exposed to free Cu2+ activities in solution ranging from 0.4 to 2,420 nM and (b) the relative importance of plant uptake and soil’s ability to supply Cu2+ to the roots. Plant Cu flux showed a hyperbolic shape, enabling to estimate the Michaelis–Menten kinetic parameters (F max and K M) for durum wheat. Plant Cu flux was then compared with soil Cu flux as assessed by the Diffusive Gradient in Thin film technique on seven soil samples. This comparison suggested that the rate-limiting process of Cu bioavailability to durum wheat would be plant uptake kinetics in most contaminated soils with the exception of moderately contaminated, calcareous soils. However, theoretical considerations targeted soil’s ability to supply Cu as the rate-limiting process in most soils for Cu (hyper-) accumulator plants with requirement larger than that of common crop species.