The core photoluminescence emission of MOVPE‐grown GaAs–Al0.33Ga0.67As core–shell nanowires is studied as function of the relevant geometrical parameter of these nanostructures, namely the shell‐thickness to core‐radius ratio hs/Rc. The energy of the dominant emission peak was compared with values of the GaAs heavy‐ and light‐hole excitons redshifted by a uniaxial tensile strain, the latter calculated assuming perfect coherence at the core/shell interface and elastic energy equilibrium within the nanowires. Good agreement is obtained for hs/Rc < 1, the intrinsic strain‐free excitonic emission being identified at 1.510 eV, and further ascribed to bound heavy‐hole excitons. For hs/Rc > 1 increasingly larger redshifts (up to ∼9 meV in excess of values calculated based on our elastic strain model) are observed, and tentatively ascribed to shell‐dependent exciton localization effects.Experimental …